let sleeping dogs lie

(proverb) don’t talk about a problem in the past that is likely to cause more difficulties now

Example Sentences:

When my brother told my parents that he thought he had had a terrible childhood, I warned him that he should let sleeping dogs lie. A huge argument followed.

A: Hey, that’s the waiter that served us two weeks ago.
B: Yeah, it is!
A: I’m going to tell him that the service was terrible last time.
B: No, don’t.
A: Why not?
B: Because you should let sleeping dogs lie. You don’t want him to spit in our food, do you?

1. come down like cats and dogs
2. lead someone on
3. call one’s dogs off
4. raining cats and dogs
5. the squeaky wheel gets the oil
6. the squeaky wheel gets the grease