leave well alone
US /liːv wɛl əˈloʊn/
UK /liːv wɛl əˈloʊn/
1.
to not try to change something that is already satisfactory or working well, because doing so might make it worse
:
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The system is working fine, so it's best to leave well alone.
•
I was going to redecorate, but my husband told me to leave well alone.