बन्धुरात्मात्मनस्तस्य येनात्मैवात्मना जित:
अनात्मनस्तु शत्रुत्वे वर्ते तात्मैव शत्रुवत्

bandhurātmātmanastasya yenātmaivātmanā jita:
anātmanastu śatrutve varte tātmaiva śatruvat

To him who has conquered his (base) self by the (divine) self, his own self is the friend; but to him who has not subdued the self, his own self acts as the foe.

Bhagavad Gita: Chapter 6, Verse 6