Diseases of the Hearts & their Cures
"Know O beloved reader that it is most important to spend one's time and energy in treating the heart, and hastening to correct and purify it from sickness and all sins. This is due to the heart occupying a great and lofty position in Islaam, for it is the place to which the Lord looks and the storehouse for tawheed, faith, and sincerity.
Actions are distinguished, one from the other, with respect to their excellence in the Sight of Allah in accordance with the condition of the heart, not by their number or form, but rather due to the strength of the caller, his or her truthfulness, his or her sincerity and the extent to which he or she prefers Allah over himself or herself.
Al-Haafidh ibn Hajr al-Asqalaanee, said: "The heart has been singled out for this because it is the leader of the body, and through the purification of the leader the subjects become purified, and with his corruption they become corrupted. So if you, O servant of Allah, with to cure your heart then it is upon you to be truthful with regards to seeking refuge with Allah and putting your trust in Him, to pray a great deal of superogatory prayers, to perform the actions of obedience to Allah frequently, to pray the night prayer while the people are sleeping, and to treat your heart by making it continuously stick to the remembrances and by befriending only the righteous ... and to frequently recite the Qur'an. And Allah will indeed allow all of this to be preserved by him."