When Imam Ali (a) appointed Shuray bin Hani as commanding officer of the vanguard of his army, which was marching towards Syria, he gave Hani the following instructions.
Day and night keep the fear of Allah in your mind. Be afraid of this alluring and vicious world, never trust it. If you do not check yourself from the desire of acquiring inordinate things then your mind will surely drive you towards losses. Therefore, have a complete watch and command over yourself and at the time of anger and annoyance see that you do not lose your temper.