어야 자다

can only sleep if X

-아/어야 names the condition without which the sleep does not happen. Two shapes appear: something that has to be there — 나는 소리가 좀 있어야 잘 수 있는데 'I need a bit of noise to fall asleep', 사람이 있어야 자는 사람 'someone who needs people around to sleep' — and a time that has to arrive: 새벽 2시 돼야 자요, 'I don't get to sleep till two'. All these lines are casual talk about sleeping habits.

Register: casual