Discipline is a valuable quality, when it is not imposed from without. In other words, self-discipline. This is the control of oneself - body, speech, mind, emotions, and thoughts.

Dhammapada
*source: translation by Max Muller (1881)

"7 He who lives looking for pleasures only, his senses uncontrolled, immoderate in his food, idle, and weak, Mâra (the tempter) will certainly overthrow him, as the wind throws down a weak tree.

8 He who lives without looking for pleasures, his senses well controlled, moderate in his food, faithful and strong, him Mâra will certainly not overthrow, any more than the wind throws down a rocky mountain."
-Chapter 1

"24 If an earnest person has roused himself, if he is not forgetful, if his deeds are pure, if he acts with consideration, if he restrains himself, and lives according to law,--then his glory will increase.

25 By rousing himself, by earnestness, by restraint and control, the wise man may make for himself an island which no flood can overwhelm."
-Chapter 2

"104, 105 One's own self conquered is better than all other people; not even a god, a Gandharva, not Mâra with Brahman could change into defeat the victory of a man who has vanquished himself, and always lives under restraint.


109 He who always greets and constantly reveres the aged, four things will increase to him, viz. life, beauty, happiness, power.

110 But he who lives a hundred years, vicious and unrestrained, a life of one day is better if a man is virtuous and reflecting.

111 And he who lives a hundred years, ignorant and unrestrained, a life of one day is better if a man is wise and reflecting."
-Chapter 8

"142 He who, though dressed in fine apparel, exercises tranquillity, is quiet, subdued, restrained, chaste, and has ceased to find fault with all other beings, he indeed is a Brâhmana, an ascetic (sramana), a friar (bhikshu)."
-Chapter 10

155 Men who have not observed proper discipline, and have not gained treasure in their youth, perish like old herons in a lake without fish.

156 Men who have not observed proper discipline, and have not gained treasure in their youth, lie, like broken bows, sighing after the past."
-Chapter 11

183 Not to commit any sin, to do good, and to purify one's mind, that is the teaching of (all) the Awakened.

184 The Awakened call patience the highest penance, long-suffering the highest Nirvâna; for he is not an anchorite (pravragita) who strikes others, he is not an ascetic (sramana) who insults others.

185 Not to blame, not to strike, to live restrained under the law, to be moderate in eating, to sleep and sit alone, and to dwell on the highest thoughts,--this is the teaching of the Awakened."
-Chapter 14

"225 The sages who injure nobody, and who always control their body, they will go to the unchangeable place (Nirvâna), where, if they have gone, they will suffer no more.

226 Those who are ever watchful, who study day and night, and who strive after Nirvâna, their passions will come to an end.


231 Beware of bodily anger, and control thy body! Leave the sins of the body, and with thy body practise virtue!

232 Beware of the anger of the tongue, and control thy tongue! Leave the sins of the tongue, and practise virtue with thy tongue!

233 Beware of the anger of the mind, and control thy mind! Leave the sins of the mind, and practise virtue with thy mind!

234 The wise who control their body, who control their tongue, the wise who control their mind, are indeed well controlled."
-Chapter 17

248 O man, know this, that the unrestrained are in a bad state; take care that greediness and vice do not bring thee to grief for a long time!
-Chapter 18

261 He in whom there is truth, virtue, love, restraint, moderation, he who is free from impurity and is wise, he is called an elder.
-Chapter 19


280 He who does not rouse himself when it is time to rise, who, though young and strong, is full of sloth, whose will and thought are weak, that lazy and idle man will never find the way to knowledge.

281 Watching his speech, well restrained in mind, let a man never commit any wrong with his body! Let a man but keep these three roads of action clear, and he will achieve the way which is taught by the wise.
-Chapter 20

"307 Many men whose shoulders are covered with the yellow gown are ill-conditioned and unrestrained; such evil-doers by their evil deeds go to hell.

308 Better it would be to swallow a heated iron ball, like flaring fire, than that a bad unrestrained fellow should live on the charity of the land...

312 An act carelessly performed, a broken vow, and hesitating obedience to discipline, all this brings no great reward.

313 If anything is to be done, let a man do it, let him attack it vigorously! A careless pilgrim only scatters the dust of his passions more widely."
-Chapter 22

"*''Comment by Muller:''
"The elephant is with the Buddhists the emblem of endurance and self-restraint. Thus Buddha himseIf is called Nâga, 'the Elephant' (Lal. Vist. p. 553), or Mahânâga, 'the great Elephant' (Lal. Vist. p. 553), and in one passage (Lal. Vist. p. 554) the reason of this name is given, by stating that Buddha was sudânta, 'well-tamed,' like an elephant. He descended from heaven in the form of an elephant to be born on earth.""
-Chapter 23

"360 Restraint in the eye is good, good is restraint in the ear, in the nose restraint is good, good is restraint in the tongue.

361 In the body restraint is good, good is restraint in speech, in thought restraint is good, good is restraint in all things. A Bhikshu, restrained in all things, is freed from all pain.

362 He who controls his hand, he who controls his feet, he who controls his speech, he who is well controlled, he who delights inwardly, who is collected, who is solitary and content, him they call Bhikshu.

363 The Bhikshu who controls his mouth, who speaks wisely and calmly, who teaches the meaning and the law, his word is sweet.


375 And this is the beginning here for a wise Bhikshu: watchfulness over the senses, contentedness, restraint under the law; keep noble friends whose life is pure, and who are not slothful."
-Chapter 25

"391 Him I call indeed a Brâhmana who does not offend by body, word, or thought, and is controlled on these three points."
-Chapter 26

also

"It is better to conquer yourself than to win a thousand battles. Then the victory is yours. It cannot be taken from you, not by angels or by demons, heaven or hell."
-Buddha

Aleister Crowley

Liber III vel Jugorum
Behold the Yoke upon the neck of the Oxen! Is it not thereby that the Field shall be ploughed? The Yoke is heavy, but joineth together them that are separate --- Glory to Nuit and to Hadit, and to Him that hath given us the Symbol of the Rosy Cross! Glory unto the Lord of the Word Abrahadabra, and Glory unto Him that hath given us the Symbol of the Ankh, and of the Cross within the Circle! ...Three are the Beasts wherewith thou must plough the Field; the Unicorn, the Horse, and the Ox. And these shalt thou yoke in a triple yoke that is governed by One Whip. Now these Beasts run wildly upon the earths and are not easily obedient to the Man. Nothing shall be said here of Cerberus, the great Beast of Hell that is every one of these and all of these, even as Athanasius hath foreshadowed. For this matter (Cerberus) is not of Tiphereth without, but Tiphereth within...The Unicorn is speech. Man, rule thy Speech! How else shalt thou master the Son, and answer the Magician at the right hand gateway of the Crown? ...The Horse is Action. Man, rule thine Action. How else shalt thou master the Father, and answer the Fool at the Left Hand Gateway of the Crown? ...The Ox is Thought. Man, rule thy Thought! How else shalt thou master the Holy Spirit, and answer the High Priestess in the Middle Gateway of the Crown? ...Thus bind thyself, and thou shalt be for ever free."

-Aleister Crowley, "Liber III vel Jugorum"

Liber AL vel Legis
"There is help & hope in other spells. Wisdom says: be strong! Then canst thou bear more joy. Be not animal; refine thy rapture! If thou drink, drink by the eight and ninety rules of art: if thou love, exceed by delicacy; and if thou do aught joyous, let there be subtlety therein!"

-Liber AL II:70

Liber Aleph
"DE VI PER DISCIPLINAM COLENDA

Consider the Bond of a cold Climate, how it maketh Man a Slave; he must have Shelter and Food with fierce Toil. Yet hereby he becometh strong against the Elements, and his moral Force waxeth, so that he is Master of such Men as live in Lands of Sun where bodily Needs are satisfied without Struggle.

Consider also him that willeth to exceed in Speed or in Battle, how he denieth himself the Food he craveth, and all Pleasures natural to him, putting himself under the harsh Order of a Trainer. So by this Bondage he hath, at the last, his Will.

Now then the one by natural, and the other by voluntary, Restriction have come each to greater Liberty. This is also a general Law of Biology, for all Development is Structuralization; that is, a Limitation and Specialization of an originally indeterminate Protoplasm, which latter may therefore be called free, in the Definition of a Pedant." -chapter 37

"DE ORDINE RERUM

In the Body every Cell is subordinated to the general physiological Control, and we who will that Control do not ask whether each individual Unit of that Structure be consciously happy. But we do care that each fulfil its Function, and the Failure of even a few Cells, or their Revolt, may involve the Death of the whole Organism. Yet even here the Complaint of a few, which we call Pain, is a Warning of general Danger. Many Cells fulfil their Destiny by swift Death, and this being their Function, they in no wise resent it. Should Hæmoglobin resist the Attack of Oxygen, the Body would perish, and the Hæmoglobin would not even save itself. How, o my Son, do thou then consider deeply of these Things in thine Ordering of the World under the Law of Thelema. For every Individual in the State must be perfect in his own Function, with Contentment, respecting his own Task as necessary and holy, not envious of another's. For so only mayst thou build up a Free State, whose directing Will shall be singly directed to the Welfare of all." -chapter 38

"DE HOC MODO DISSOLUTIO

Here therefore will I write down the Answer to this Indictment of our Wisdom; that every Act of Will is to be made in its Perfection, which State is to be attained according to these Conditions: firs, those of its own Law; second, those of its Environment. Judge thine own Case individually, each as it pleadeth; for there is no Cannon or Code, since every Star hath its own Law diverse from every other. Now there is the Restraint of Conflict which is Impotence and Disruption; the the Restraint of Discipline is a Fortification of the Will by Repose and by Preparation, as a Conqueror resteth his Armies, and feedeth them, and looketh to their Furniture and to their Spirit, before he joineth the Battle. Also, there is the Restraint of Art, which includeth that other of Discipline, and its Nature is to adorn the Will and to admire its Strength and its Beauty, and to enjoy its Victory by Anticipation in full Confidence, not fearful of Time that robbeth them that are ignorant concerning him, how he is but Mirage and Illusion, incapable to besiege the Fortress of the Soul. Work thou thy Will, knowing (as I said aforetime by the Mouth of Eliphas Levi Zahed), thyself Omnipotent, and thine Habitation Eternity. O my Son, attend well this Word, for it is an Heirloom, and a Ring of Ruby and Emerald in thine Inheritance." -chapter 196

Magick Without Tears
"Shameful confession, one of my own Chelas (or so it is rather incredibly reported to me) said recently: "Self-discipline is a form of Restriction." (That, you remember, is "The word of Sin ...".) Of all the utter rubbish! (Anyhow, he was a "centre of pestilence" for discussing the Book at all.) About 90 % of Thelema, at a guess, is nothing but self-discipline. One is only allowed to do anything and everything so as to have more scope for exercising that virtue."

-Aleister Crowley, Magick Without Tears, chapter 70


*"What is true for every School is equally true for every individual. Success in life, on the basis of the Law of Thelema, implies severe self-discipline."

-Aleister Crowley, Magick Without Tears, chapter 8

New Testament
"Be swift to hear, slow to speak, slow to wrath."
-James 1:19

"If anyone among you thinks himself to be religious while he doesn't bridle his tongue, but deceives his heart, this man's religion is worthless."
-James 1:26

"33 Either make the tree good, and its fruit good, or make the tree corrupt, and its fruit corrupt; for the tree is known by its fruit.

34 You offspring of vipers, how can you, being evil, speak good things? For out of the abundance of the heart, the mouth speaks.

35 The good man out of his good treasure brings out good things, and the evil man out of his evil treasure brings out evil things.

36 I tell you that every idle word that men speak, they will give account of it in the day of judgment.

37 For by your words you will be justified, and by your words you will be condemned."
-Matthew 12:33-37

"10 He summoned the multitude, and said to them, "Hear, and understand.

11 That which enters into the mouth doesn't defile the man; but that which proceeds out of the mouth, this defiles the man."
-Matthew 15:10-11

"15 Peter answered him, "Explain the parable to us."

16 So Jesus said, "Do you also still not understand?

17 Don't you understand that whatever goes into the mouth passes into the belly, and then out of the body?

18 But the things which proceed out of the mouth come out of the heart, and they defile the man.

19 For out of the heart come forth evil thoughts, murders, adulteries, sexual sins, thefts, false testimony, and blasphemies.

20 These are the things which defile the man; but to eat with unwashed hands doesn't defile the man."
-Matthew 15:15-20

"7 Woe to the world because of occasions of stumbling! For it must be that the occasions come, but woe to that person through whom the occasion comes!

8 If your hand or your foot causes you to stumble, cut it off, and cast it from you. It is better for you to enter into life maimed or crippled, rather than having two hands or two feet to be cast into the eternal fire.

9 If your eye causes you to stumble, pluck it out, and cast it from you. It is better for you to enter into life with one eye, rather than having two eyes to be cast into the Gehenna of fire."
-Matthew 18:7-9

"7 For God didn't give us a spirit of fear, but of power, love, and self-control.

8 Therefore don't be ashamed of the testimony of our Lord, nor of me his prisoner; but endure hardship for the Good News according to the power of God."
-2 Timothy 1:7

"12 Whoso loveth discipline loveth knowledge, but he that hateth reproof is brutish."
-Proverbs 12:1


Upanishads
Mundaka Upanishad
note: Eknath Easwaran translation

"11 But those who are pure in heart, who practice meditation and conquer their senses and passions, shall atain the immortal Self, Source of all light and source of all life."
-Mundaka Upanishad, chapter I, line 11 (trans. by Eknath Easwaran)

"5 By truth, meditation, and self-control one can enter into this state of joy and see the Self shining in a pure heart."
-Mundaka Upanishad, chapter III, section 1, line 5 (trans. by Eknath Easwaran)

"4 Not by the weak, not by the unearnest, not by those who practice wrong disciplines can the Self be realized. The Self reveals Himslf as the Lord of Love to the one who practices right disciplines."
-Mundaka Upanishad, chapter III, section 2, line 4

Bhagavad Gita
note: Mahatma Gandhi translation

"60 For, in spite of the wise man's endeavour, O Kaunteya, the unruly senses distract his mind perforce.

61 Holding all these in check, the yogi should sit intent on Me; for he whose senses are under control is secure of understanding.

...

64 But the disciplined soul, moving among sense-objects with the senses weaned from likes and dislikes and brought under the control of Atman, attains peace of mind.

65 Peace of mind means the end to all ills, for the understanding of him whose mind is at peace stands secure.

66 The undisciplined man has neither understanding nor devotion; for him who has no devotion there is no peace, and for him who has no peace whence happiness?

67 For when his mind runs after any of the roaming senses, it sweeps away his understanding, as the wind a vessel upon the waters.

68 Therefore, O Mahabahu, he, whose senses are reined in on all sides from their objects, is the man of secure understanding."
-Chapter 2

"7 But he, O Arjuna, who keeping all the senses under control of the mind, engages the organs in Karma yoga, without attachment—that man excels.

...

41 Therefore, O Bharatarshabha, bridle thou first the senses and then rid thyself of this sinner, the destroyer of knowledge and discrimination."
-Chapter 3

"3 Those who have attained perfect renunciation are free from any sense of duality; they are unaffected by likes and dislikes, Arjuna, and are free from the bondage of self-will...

...

22 Pleasures conceived in the world of the senses have a beginning and an end and give birth to misery, Arjuna. The wise do not look for

23 happiness in them. But those who overcome the impulses of lust and anger which arise in the body are made whole and live in joy.

24 They find their joy, their rest, and their light completely within themselves. United with the Lord, they attain nirvana in Brahman."
-Chapter 5 (Eknath Easwaran translation)


"5 Reshape yourself through the power of your will; never let yourself be degraded by self-will. The will is the only friend of the Self, and the will is the only enemy of the Self

6 To those who have conquered themselves, the will is a friend. But it is the enemy of those who have not found the Self within them.

7 The supreme Reality stands revealed in the consciousness of those who ahve conquered themselves. They live in peace, alike in cold and heat, pleasure and pain, praise and blame.

8 They are completely fulfilled by spiritual wisdom and Self-realization. Having conquered their senses, they have climbed to the summit of human consciousness. To such people a clod of dirt, a stone, and gold are the same.

9 They are equally disposed to family, enemies, and friends, to those who support them and those who are hostile, to the good and the evil alike. Because they are impartial, they rise to great heights.

10 Those who aspire to the state of yoga should seek the Self in inner solitude through meditation. With body and mind controlled they should constantly practice one-pointedness, free from expectations and attachment to material possessions.


17 Those who are disciplined in eating and sleeping, work and recreation, will come to the end of sorrow through meditation.


35 It is true that the mind is restless and difficult to control. But it can be conquered, Arjuna, through regular practice and detachment.

36 Those who lack self-cotnrol will find it difficult to progress in meditation; but those who are self-controlled, striving earnestly through the right means, will attain the goal."
-Chapter 6 (Eknath Easwaran translation)

Paramahansa Yogananda
Man's Eternal Quest
"People seldom learn true self-control (...). To be able to do things when and because you ought to do them, and to refrain from doing what you know is injurious - these are keys to real success and happiness."
-Paramahansa Yogananda, Man's Eternal Quest, P.78.


"(...) the only way to health and happiness, and the sanest way, is self-control.
-Paramahansa Yogananda, Man's Eternal Quest, P.104.


"Mankind is like a large zoo - so many people behaving so differently, most of them having no real control over themselves."
-Paramahansa Yogananda, Man's Eternal Quest, P.145.


"The second way to cosmic consciousness is the way of self-discipline. (...) Enjoy things, but don't be attached to them. Be free. Be pleasant and self-controlled. Avoid becoming a slave to wrong habits, and act only according to your righteous convictions."
-Paramahansa Yogananda, Man's Eternal Quest, P.170.


"God does not bestow great spiritual powers on devotees until they show Him they have conquered their human weaknesses. Otherwise they might hurt other persons, even destroy whole nations, by misuse of the divine might."
-Paramahansa Yogananda, Man's Eternal Quest, P.234.


Other quotations
“Each soul is potentially divine. The goal is to manifest this divinity within by controlling nature: external and internal. Do this either by work, or by worship, or psychic control, or philosophy – by one, or more, or all of these – and be free. This is the whole of religion. Doctrines, or dogmas, or rituals, or books, or temples, or forms, are but secondary details.”
-Swami Vivekananda, Raja-Yoga, cover


"He who conquers self conquers all."
-Swami Vivekananda


"Freedom is not procured by a full enjoyment of what is desired, but by controlling the desire."
-Epictetus, Discources


"He who has control over himself, who is of determined mind, will succeed in life."
-Teachings of Babaji, P.91.


"...For the love of God, discipline yourself in body and spirit so that you preserve your health as long as you can."
-The Cloud of Unknowing, P.101.


"In reading the lives of great men, I found that the first victory they won was over themselves...self-discipline with all of them came first."
-Harry S. Truman


"Nothing of importance is ever achieved without discipline. I feel myself sometimes not wholly in sympathy with some modern educational theorists, because I think that they underestimate the part that discipline plays. But the discipline you have in your life should be one determined by your own desires and your own needs, not put upon you by society or authority."
-Bertrand Russell


"Right discipline consists, not in external compulsion, but in the habits of mind which lead spontaneously to desirable rather than undesirable activities."
-Bertrand Russell, ''On Education: Especially in Early Childhood''


"Rule your mind or it will rule you."
-Horace


"The first and greatest victory is to conquer yourself; to be conquered by yourself is of all things most shameful and vile."
-Plato


"Talent without discipline is like an octopus on roller skates. There's plenty of movement, but you never know if it's going to be forward, backwards, or sideways."
-H. Jackson Brown, Jr., Author


"It is not enough to have great qualities; We should also have the management of them."
-La Rochefoucauld, French cardinal


"I think the guys who are really controlling their emotions ... are going to win."
-Tiger Woods


"Nothing is more harmful to the service, than the neglect of discipline; for that discipline, more than numbers, gives one army superiority over another."
-George Washington


"Be not angry that you cannot make others as you wish them to be, since you cannot make yourself as you wish to be."
-Thomas á Kempis, Roman Catholic monk


"If you will discipline yourself to make your mind self-sufficient you will thereby be least vulnerable to injury from the outside."
-Critias of Athens


"The individual who wants to reach the top... must appreciate the might and force of habit. He must be quick to break those habits that can break him—and hasten to adopt those practices that will become the habits that help him achieve the success he desires."
-J. Paul Getty


"Some people regard discipline as a chore. For me, it is a kind of order that sets me free to fly."
-Julie Andrews (Mary Poppins)