Chapter VI · Śloka 23
तं विद्याद्दुःखसंयोगवियोगं योगसञ्जितम् |
स निश्चयेन योक्तव्यो योगोऽनिर्विण्णचेतसा ||
स निश्चयेन योक्तव्यो योगोऽनिर्विण्णचेतसा ||
taṃ vidyād duḥkha-saṃyoga-viyogaṃ yoga-sañjitam |
sa niścayena yoktavyo yogo 'nirvinna-cetasā ||
sa niścayena yoktavyo yogo 'nirvinna-cetasā ||
Let it be known: that disengagement from union with suffering is called yoga. This yoga is to be practiced with determination and without despondency of heart.
Krishna gives yoga one of its most direct definitions: viyoga from duḥkha-saṃyoga — disentanglement from the habitual coupling with suffering. And immediately adds the instruction for its practice: niścaya, unwavering resolve, and a heart that refuses to give in to discouragement.