不要惹是生非

Don't agitate a potential source of trouble.

A: You'd better not say anything to the owner of the building about painting your apartment. If I were you I'd let sleeping dogs lie. The last time you asked him to do some repairs, he raised your rent.

B: You're telling me not to make trouble if I don't have to, but I'm going to risk making him angry. I can no longer stand to look at the paint peeling off the walls.