고 힘내다

get your strength up

힘내다 is summoning energy or keeping your spirits up, and -고 names what supplies it. Five of the eight lines here pair it with eating — 비타민 먹고 힘내서, 꿀 먹고 힘내려구 — and the others with listening to a song or seeing someone. The tone is affectionate and encouraging; 힘내 on its own is the standard 'hang in there'.

Register: warm, encouraging