horses for courses

change horses in midstream

To change one's plan or approach when an effort is already underway or at another inopportune time.

drive a coach and horses through

To spoil, break or render ineffective (a rule, plan or agreement).

hold one's horses

To be patient; to wait.

swap horses in midstream

Alternative form of change horses in midstream.

wild horses

A force not subject to human control and normally stronger than a man.