My appendix mare used to rush fences like it was her only job in the world. lol She'd see a fence and away she'd charge. If I stopped her, it only made her more tense and braced. I did as exactly as Spyder and MI Eventer are trying to get across. I can't count the number of times I had to do a circle or two before the next jump. My trainer told me I was not allowed to pull on her face, just circle her while trying to encourage her to slow down by the change in my body. Once she did, she was allowed to walk. Boy was that an experience for me at the time. Here is my horse, blasting towards this fence(not out of control, but not steady by any means), and I was only allowed to slow her with my body, otherwise leave her face completely alone. The more times I did that, the fences got boring the more boring I was, and in time I learned a very special and important skill. Riding with my body, not my hands, and teaching my horse to feel me.
She'll never look like a slow-mo hunter type mover, but now she stays right with me due to the communication of my body, which taught her how to relax.
In riding, a horse's energy is like a river- guided by the banks but not stopped by them.