Verse
बन्धुरात्मात्मनस्तस्य येनात्मैवात्मना जितः ।अनात्मनस्तु शत्रुत्वे वर्तेतात्मैव शत्रुवत् ॥
To the man is his self a friend in whom the (lower) self has been conquered by the (higher) self, but to him who is not in possession of his (higher) self, the (lower) self is as if an enemy and it acts as an enemy.
Gītā 6·6