How do you control a horse that has a lot of energy (like a lot) without pulling in her mouth too much?

I do a lot of circling and yielding the hind then front and then move them both to the side and the same time and repeat
Keep them busy. Don't allow them to become bored. Multiple transitions within gaits and in or out of gaits. Circles, leg yeilding. Maybe even set up cones and make a game out of it.
Have you tried lunging him before riding? This will get him in the right mind set for working, he'll have less energy, and will help him concentrate on your movements rather than just wanting to run. If he's still energetic half halts while riding is great, and if he doesn't slow down, circling into a tighter circle always gets them to slow down.
I do a lot of trot hault transitions my horse has some thorobred and really likes to run, but you can eventually build the full hault into a half hault.
Also try not to pull, but half halt every few steps to remind her to balance and sit up and that she can't just go blazing around whenever she feels like it.
I do many circles, I talk to him and work a lot! He has to spend a lot of energy so work a lot as well! But he also have to respect what you ask him to do! I try to pull as less as possible because if we pull both, he's going to accelerate more again... :)
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