leave well (enough) alone

To refrain from changing, disturbing, or becoming involved in something so as to avoid unintentionally causing (or worsening) problems. To be honest, you're better off leaving well alone at this point. She's so angry that anything you say will just make things worse. Messing with the registry can cause catastrophic problems for your computer. If it isn't already totally busted, I would leave well enough alone.

Also, let well enough alone. Do not try to change something lest you make it worse. For example, This recipe has turned out fine in the past, so leave well enough alone. The idea behind this expression dates from ancient Greek times, specifically Aesop's fable 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. Put as let well alone from the early 1700s, it was first recorded as let well enough alone in 1827. Also see let sleeping dogs lie.

If you leave well alone, you do not interfere in something, because it is all right as it is and you might make it worse. He knew when to leave well alone and when to interfere. Gordon knows his business, he says, and I should just leave well alone.