if it ain't broke don't fix it

Don't meddle with something that's functioning adequately. For example, So long as they like our proposal let's not change it; if it ain't broke don't fix it. This folksy and deliberately ungrammatical expression dates from the mid-1900s. For a synonym, see leave well enough alone.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.