नात्यश्नतस्तु योगोऽस्ति न चैकान्तमनश्नतः । न चाति स्वप्नशीलस्य जाग्रतो नैव चार्जुन ॥
nātyaśnatastu yogo'sti na caikāntamanaśnataḥ | na cāti svapnaśīlasya jāgrato naiva cārjuna ||
Translation
Yoga is not for one who eats too much or who eats too little; not for one who sleeps too much or who remains awake too long, O Arjuna.
Interpretation
Krishna introduces the principle of moderation as the foundation of successful practice. Four extremes are named: excessive eating, excessive fasting, excessive sleep, and excessive wakefulness. Each extreme creates imbalance in the body-mind system that makes sustained meditation impossible. The overeater's mind is dull and heavy; the undereater's mind is agitated and weak. The oversleeper lacks alertness; the insomniac lacks rest. Yoga requires a clear, balanced instrument.