sleep on it意思是：好好想想，徹夜思考，仔細權衡，跟睡覺沒關係。遇到類似的要你做決定或表態的情景時，可以用“I’ll sleep on it.”。
examples:
1. You don’t have to give me your decision now. Sleep on it, and let me know tomorrow.
2. Don’t give me an answer now—sleep on it and we can talk some more later this week.
3. We are all tired and none of us can think straight, so why don’t we go home and sleep on it, eh?
A: You don’t have to answer right now.
B: Okay. I will sleep on it.
A:You shouldn’t miss this chance.
B:Yeah. I’ll sleep on it. I can give you my answer tomorrow.
A:Do you think we should agree to the new contract?
B:I Don’t know. I’ll sleep on it.
類似意思：
I’ll think it over.
Let me think it over.
I’ll give it some thought.
