if it isn't broken, don't fix it

If something is performing or functioning well enough, there's no need to change or interfere with it (as you may introduce new problems as a result.) A variant of the more common phrase "If it ain't broke, don't fix it." A: "We don't really need to implement these ridiculous changes, do we? Our current method is working just fine." B: "Right. If it isn't broken, don't fix it." Nothing's wrong with the washing machine, so why do you keep tinkering with it? If it isn't broken, don't fix it! Things are finally running smoothly in our department, so, please—if it isn't broken, don't fix it!