It is the usual way of Almighty, Allah that what is required most is proivded most. The more pressing the need for a thing, the more plentiful is the provision for the same. Looking at the most essential necessities of life, such as breathing, water and air, it will be observed that Almighty Allah has created them in great abundance. It is, however, Ikhlaas (purity of intention) that determines the value of things in the eye of Almighty Allah. The greater the Ikhlaas in an action the greater will be its weight and, likewise, less the Ikhlaas and devotion, the lesser the weight. For the attainment of this Ikhlaas, nothing is more effective than this Kalimah. That is why it is also known as purifer of hearts. (Jalaul Qulub). For it s purifying effect, Sufis prescribe  zikr of this Kalimah and advise its recitation as a daily routine, not only in hundreds but in thousands of times. Mulla Ali Qari (Rahmatullah alaih) writes that a disciple once compalined to his Shaikh that, despite doing zikr, his heart remained inattentive. The Shaikh replied : "Go on with your zikr firmly, and thank Almighty Allah for His grace that He enabled a part of your body, i.e. the tongue, to remain busy in His Zikr, and pray to Allah for a devoted heart." A similar incident is related in Ihyaa-ul  Uloom about Abu Usman Maghribi, who gave the same reply on a similar complaint made by one of his disciples, and he prescribed the same cure. As a matter of fact, zikr is the best remedy for indolence of the heart. Almighty Allah says in His Book, "If you show gratitude to me, I will grant even more than before." Likewise the hadith says, " Zikr of Almightly Allah is a great blessing; and be thankful to Him in as much as He has enabled you to do His zikr."