let well enough alone
To be satisfied with what is good enough; not try to improve something because often that might cause more trouble.
John wanted to make his kite go higher, but his father told him to let well enough alone because it was too windy.
Ed polished up his car until his friends warned him to leave well enough alone.
Ethel made a lot of changes in her test paper after she finished. She should have let well enough alone, because she made several new mistakes.
Compare: LET RIDE.