Bhagavad Gita 6.5

उद्धरेदात्मनाऽऽत्मानं नात्मानमवसादयेत्। आत्मैव ह्यात्मनो बन्धुरात्मैव रिपुरात्मनः

uddhared ātmanātmānaṁ nātmānam avasādayet ātmaiva hyātmano bandhur ātmaiva ripur ātmanaḥ

Let him raise the self by the Self and not let the self become depressed; for verily is the Self the friend of the self, and also the Self the self's enemy;