sleep on it意思是：好好想想，彻夜思考，仔细权衡，跟睡觉没关系。遇到类似的要你做决定或表态的情景时，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.
类似意思：
I’ll think it over.
Let me think it over.
I’ll give it some thought.
