As a rider, you must slowly and methodically show your horse what is appropriate. You also have to discourage what's inappropriate, not by making the inappropriate impossible, but by making it difficult so that the horse himself chooses appropriate behavior. You can't choose it for him; you can only make it difficult for him to make the wrong choices. If, however, you make it impossible for him to make the wrong choices, you're making war.

Faraway Horses: The Adventures and Wisdom of One of America's Most Renowned Horsemen (ed. 2003)