Chapter 6 · The Yoga of Meditation · Krishna said
Bhagavad Gita 6.23 — Yoga is freedom from sorrow
तं विद्याद् दुःखसंयोगवियोगं योगसंज्ञितम्। स निश्चयेन योक्तव्यो योगोऽनिर्विण्णचेतसा ॥
taṃ vidyād duḥkhasaṃyogaviyogaṃ yogasaṃjñitam | sa niścayena yoktavyo yogo'nirviṇṇacetasā ||
Meaning
— know that to be yoga: freedom from all contact with sorrow. This yoga should be practised with firm resolve and a mind that does not lose heart.