change horses in midstream, don't

Also, don't swap horses in midstream. It's unwise to alter methods or choose new leaders during a crisis, as in I don't hold with getting a new manager right now—let's not swap horses in midstream. This expression was popularized (although not originated) by Abraham Lincoln in a speech in 1864 when he discovered that the National Union League was supporting him for a second term as President.

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