leave/let well enough alone

Do not try to improve matters lest you make them worse. This idea was stated in ancient Greek times. In Aesop’s fable, the fox refused the hedgehog’s offer to remove its ticks, “lest by removing these, which are full, other hungry ones will come.” There is a medieval French version of the saying, Assez est bone, lessez ester (It is good enough, let it be). An English proverb for many centuries, the phrase became the motto of Sir Robert Walpole, prime minister from 1715 to 1717 and again from 1721 to 1742. A slangy twentieth-century Americanism meaning the same thing is if it ain’t broke don’t fix it. Reporting on a meeting between West German Chancellor Helmut Kohl and President George H.W. Bush concerning the future of NATO in view of German unification, Strobe Talbott wrote, “They both believe in the old adage, ‘If it ain’t broke, don’t fix it.’ NATO has kept the peace for 40 years, and there’s no reason to believe it can’t do so for another 40” (Time, July 2, 1990). See also let sleeping dogs lie.