Smile!

Laughing moderately can act as a cure or therapy for depression and sadness. It has a strong influence on keeping the soul light and the heart clear. Abu Darda (radiAllahu anhu) said, 'I make it a practice to laugh in order to give rest and comfort to my heart. And the noblest of people, Muhammad (sallalahu Alayhi Wasalam), would laugh, sometimes until his molars became visible.'

Laughing is an efficacious way to achieve comfort and light heartedness, but keep in mind that, as in other things, you should not be immoderate. The Prophet (sallalahu Alayhi Wasalam) said:
'Do not laugh excessively, for verily, excessive laughter kills the heart.'

What is called for is moderation.

He (sallalahu Alayhi Wasalam) further said: 'And if you smile in the face of your brother, then this is a form of charity.'

Allah tells us: "So he, Sulaiman, smiled, amused by her speech."
[surah An-Naml � Ayah 19].

Among the pleasures of Paradise will be laughter:
"But this Day those who believe will laugh at the disbelievers."
[surah Al-Mutaffifin � Ayah 34].

The Arabs would hold in high esteem the one known for his smile and laughter. They believed this to proclaim a generous personality, a person with a noble disposition and a clear mind. The truth is that the principles of Islam are based on moderation and on good measure, whether it be in matters of belief, worship, manners, or conduct. Islam does not condone a rigid, frowning expression, nor does it condone a constant playful giddiness; rather what it does promote is seriousness when it is called for.

Bearing a gloomy mien and a frowning countenance are marks of a lowly character, a troubled nature, and hot-headedness.

"Then he frowned and he looked in a bad tempered way�" [surah Al-Muddaththir � Ayah 22]. The Prophet (sallalahu Alayhi Wasalam) advised the people:
'Do not disparage (underestimate) any good deed (no matter how small it is), even if that deed was to meet your brother with a friendly countenance.'

Ahmed Ameen said in his book Fayd al-Khatir:
"People who are always smiling not only make their own lives more joyful, but what is more, they are more productive people in their work and have a greater ability to live up to their responsibilities. They are more prepared to face difficulties and to find expedient solutions for them. They are prolific workers who benefit themselves and others."

If I were given a choice between having status in society and plentiful money, or between having a happy, radiant, smiling self, I would choose the latter.
For what is great wealth if it begets misery? And what is high position if what comes with it is constant gloominess? And what good is the most beautiful wife if she transforms her house into a living hell?
Much better than her - a thousand times at least - is a wife who has not reached such a pinnacle of beauty, but nonetheless has made her house to be a paradise.

The human being by his very nature is a smiling entity, were it not for those things that counteract this natural disposition, such as greed and selfishness, evils that contribute to his frowning. As such he is an anomaly and at odds with the natural harmony of all that surrounds him. Therefore the person whose heart is sullied cannot see things as they truly are. Every person sees the world through himself, by his actions, thoughts, and motives. So if our action is noble, our thought is clean, and our motive is honourable, then the spectacles through which we see the world will be clean, and the world will appear as it really is - a beautiful creation. If the spectacles become dirty, and their lenses stained, then everything will seem to be black and morbid.