Bhagavad Gita 6.5

उद्धरेदात्मनात्मानं नात्मानमवसादयेत् |
आत्मैव ह्यात्मनो बंधुरात्मैव रिपुरात्मन:

Translation

Elevate yourself through the power of your mind, and not degrade yourself, for the mind can be the friend and also the enemy of the self.