Chapter 6 - Verse 23

तं विद्याद् दुःखसंयोगवियोगं योगसंज्ञितम् ।
स निश्चयेन योक्तव्यो योगोऽनिर्विण्णचेतसा ॥ २३ ॥

taṃ vidyād duḥkhasaṃyogaviyogaṃ yogasaṃjñitam .
sa niścayena yoktavyo yogo’nirviṇṇacetasā .. 23 ..


This severance from union with pain, be it known, is called union (Yoga). That Yoga must be practised with determination and with undepressed heart.
Read the commentary
Severance from union with pain is called Yoga (which means union) by a sort of irony. Having thus concluded speaking of the effect of Yoga, the Lord again refers to the necessity of it, with a view to show that determination and non-depression (self-reliance) are necessary means to Yoga. That Yoga: the Yoga which can produce the result described above.