Bhagavad Gita 6.23

तं विद्याद् दुःखसंयोगवियोगं योगसंज्ञितम् |
स निश्चयेन योक्तव्यो योगोऽनिर्विन्नचेतसा

Translation

That state of severance from union with misery is known as Yog. This Yog should be resolutely practiced with determination free from pessimism.