It is narrated from the eighth Shia Imam, Ali ibn Musa Al-Ridha/reza (AS) who said: The best servants of Allah (SWT) are those who:

Whenever they do a good deed, they become happy, and whenever they do a mistake or bad act, they repent (to God). Whenever something is given to them, they are thankful, and whenever they are in difficulty, they remain patient; and whenever they get angry, they forgive [1].

[1] Mosnad Al-Imam Al-Ridha (AS), Vol. 1, Page 284.

Source: en.shafaqna.com