Meaning/Usage: To take time to think about something.
Explanation: Some people report that they think more clearly after a good night sleep. Also, some people say they often times regret a decision they have made. When something is important, making a decision after a good night sleep is a good practice.
I've been thinking about this problem for two hours. I think I will sleep on it. It might come to me in the morning.
I don't think I can decide now. Let me sleep on it and I'll tell you my answer tomorrow.
I'm going to need to sleep on it. I don't want to rush my answer right now.
A:
Do you know if you are going to buy the leather set or the cashmere set?
B:
I've been thinking about it for three hours. I really can't decide.