Bhagavad Gita · 6.23

तं विद्याद्दुःखसंयोगवियोगं योगसञ्ज्ञितम्।स निश्चयेन योक्तव्यो योगोऽनिर्विण्णचेतसा॥

taṁ vidyād duḥkha-saṁyoga-viyogaṁ yoga-sañjñitam sa niśhchayena yoktavyo yogo 'nirviṇṇa-chetasā

Let that be known as yoga — the severance of union with suffering. This yoga should be practiced with determination and an unwearied mind.

— Bhagavad Gita 6.23

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)