The following is Imaam Sufyaan’s (R) letter…(Excellent)

My brother, use the time you have between dawn and sunrise to contemplate the previous day!
Remain steadfast on the good deeds you performed the previous day, and abandon anything you did out of disobedience to Allah! (Subhaanahu wa Ta’aala). Do not repeat the same mistakes, for you do not know whether or not you will live for the rest of your day! As long as you are alive, the option of repentance is available to you…! but refraining from sinning is easier for you than trying to perform sincere repentance. Sincere repentance involves regret and a firm resolve never to repeat the same sin again…

Wherever you are, fear Allah… ! If you perpetrated a sin in secret… then repent to Allah in secret. And if you perpetrated a sin out in the open, then repent to Allah out in the open. Do not let one sin lead to another(so that they pile up onto one another). Cry frequently and as much as you are able to, and do not laugh (frequently), for you were not created without purpose.

Join ties with and be kind to your family, your relatives, your neighbors, and your brothers. When you intend to show mercy, show mercy to the poor, orphans, and to the weak… If you intend to give charity… or to perform a good deed, then do it right away…! before the shaytan (devil) positions himself between you and the execution of what you intended to do.

Act always with a good intention…! Eat with a good intention and Drink with a good intention. Do not be miserly, for miserliness corrupts a person’s religion. Do not promise someone something and refrain from fulfilling your promise, for, in that case, the love you will have gained through your promise will be replaced by hate. Do not feel rancor in your heart towards your Muslim brother… ! for Allah does not accept repentance from a person if there is rancor and malice between him and his Muslim brother. Do not be angry, for anger is like a shaver… just as a shaver shaves off hair, anger shaves off good deeds (unless one becomes angry for the sake of Allah (Subhaanahu wa Ta’aala).

Make it a practice to extend greetings of peace to every Muslim, for if you do so, hatred, deception, and rancor will all be purged from your heart. Shake hands with your Muslim brothers and you will, as a result, become loved by the people…!

Remain in a constant state of purity (by performing ablution whenever you pass wind or empty your bowels) and, as a result, you will be loved by the Al-Hafazah (the angels who record your deeds).

Love only for the sake of Allah, and Hate only for the sake of Allah: If you do not possess these two qualities, it means that you have on you the mark of a hypocrite {!}

Abridged from:-The Biography of Sufyaan ath-Thauree (Rahimahullaah), p#175-176