Know that (the heart of) a person of sound mind cannot be free of sadness, because he remembers his previous sins, therefore becomes saddened, he thinks about his negligence, reflects on what the scholars and the righteous have said, as a result he becomes sad for not taking heed.
Malik ibn Dinar said, "If a heart is devoid of sadness, it will become desolate. Just as a house becomes desolate if no one resides in it." [Abu Nuaym, Al-Hilyah]
Ibrahim ibn Isa said, "I have not seen a person with as much sadness as al-Hasan; whenever I see him, I assume that he has just recently been afflicted with a trial."
Malik ibn Dinar said, "As much as you grieve for this world, the fear of the Day of Judgement leaves your heart." Thus, as it is evident that sadness accompanies the heart of the righteous, excessive sadness therefore should be avoided. That is because one should feel sad regarding what he has missed, and I have already clarified the way to recant.
It was mentioned in a hadith, "The rest of the life of a believer is invaluable, he can recant in it what he has missed." If sadness is related to something that cannot be recanted then it is of no use, however if it is related to a religious matter then he should make it up with the aid of hoping for the Graciousness and Mercifulness of Allah (swt). On the other hand if one has sadness in regards to worldly matters and whatever he misses from it, then that is an evident loss, a wise person should rid himself of that.
The best of the cures for sadness is to know that one cannot bring back what he has missed, rather by feeling sad he is adding another misfortune to the already existing misfortune ultimately making two misfortunes. Also a misfortune should not be made heavier by being saddened by it, rather it should be eased and pushed away. Ibn Amr said, "If Allah takes something away from you, get busy with anything that will not make you think about it." In addition, what Allah gives you instead of what was taken away from you makes that easier. However, if there is nothing that can make the matter easier, then one should struggle to push away sadness from his heart.
Know that what calls to sorrow and sadness is Hawa not the mind, simply because the mind does not call to that which is not useful. One should know that the matter, eventually, will get easier after some time, therefore he should strive to bring forward that which is supposed to happen then (i.e. comfort) so that he relaxes during the time of difficulty until such ease and comfort is achieved. One of the things that make sorrow and sadness disappear is knowing that it is useless, believing in its reward and remembering those who are afflicted with worse misfortunes.
The Virtue of the Mind
Dispraise of Hawa (desires)
The Difference Between the Perspective of Mind and the Perspective of Hawa
Averting Passionate Love (Ishq)
Averting Gluttony (Sharah)
Refusing to take a Position of Authority in this world
Prohibition on Squandering
Elucidation on the Amount of Earnings and Expenditure
Dispraise of Lying
Averting Riya (Insincerity and Pretentiousness)
Averting Excessive Thinking
Averting Excessive Sadness
Averting Ghamm (Grief) and Hamm (Worry)
Averting Excessive Fear and Cautiousness of Death
Averting Excessive Happiness
Identifying One's Flaws
Motivating a Low Endeavor
Disciplining and Handling Family and Slaves
Consorting with People
Flawlessness of Character