I've had Kelty, a 5 year old green quarter horse, for nearly a year. He's very relaxed in the arena, and stops, backs up, walks, turns, and laterals with the softest touch or shift of weight. In the arena, he has no problem with stopping and holding.
But the second we step outside that gate, it is all nerves and trying to walk off without permission, and when that isn't allowed, he just pivots in circles, head tossing the whole way.
I know this behavior is disrepectful and potentially dangerous, but I am at a complete loss as to how to counter it.
Any ideas are appreciated..