change horses in midstream, don't

Idioms  

1. 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.

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