Human soul enjoining unto evil opposing God given nature of man challenges its peace. Contentment and avoiding extravagance can be considered as an agent against such vices as cupidity, avarice, lie, selfishness and dependence to earthly life and as a support for mental peace in life. In this paper, using library - based, analytic - descriptive method, contentment and cupidity have been studied firstly and, then, the correlation between contentment and mental peace has been proved on the basis of Imam Alis (a) speeches in Nahj al-Balaghah and psychological principles.