Leave/let well enough alone informal verb phrase
Try to avoid to change something because doing something else could make things worse
I could do it again, but I let well enough alone.
I should have left well enough alone, but I didn't. As a result, my project was damaged by myself.
The verb "leave/let" should be conjugated according to its tense.
The story of this phrase is derived from ancient Greek times, specifically Aesop's fable. It's about a fox who refused a hedgehog's offer to take out its ticks lest, by removing those that are full, other hungry ones will replace them. It was first recorded in 1827.
A group of bad or sinful people
You'd better stay away from them. They are a nest of vipers.