Sleep on it

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."
A: "Why don't you sleep on it."