Changing Horses in Midstream

[Tamawa]

What does this mean ? and Where does it come from

[incitatus]

the expression is don't change horses in midstream. It means when you are already committed to one plan, don't start another until the first is finished. Often applied to electoral politics. It comes from crossing a river on a ford...if you tried to change horses in midstream you would end up getting wet. (in the days of tollroads, or the pony express in the us, fresh horses were kept at regular intervals. Riders would exchange horses and continue. Fords were natural staging posts.)