Mine took off with me a few weeks ago and I was petrified! The lane was too small to turn in and we were going so fast I could see him slipping and both of us going over. I started by dropping the contact and trying to slow him with my seat and weight. I tried half-halting. I tried bending his head to the right. In the end, we were going downhill at top speed and I just sat back and kept playing with the reins praying we would stop. Eventually the fence around the school was looming towards us with no where to go but over it, so I closed my eyes and
heaved like my life depended on it. I'll never ever do that again! I didn't think he could go any faster - it turned out we were just having a steady canter! He really started racing, neck stretched out, mane flying, and I wound up leaning right forward, arms wrapped around his neck, tears whipping from my eyes with the speed, feet jammed into stirrups, too freaked out to even swear under my breath. This fence was
speeding towards us now, and I could see a couple of horses in there schooling. I was having visions of Salsa jumping the fence and landing on one of them, or leaping the fence, shooting across the school, leaping out again and continuing all the way to his stable! Or worse, out onto the main road.
Fortunately, he decided he didn't want to jump and slammed on the breaks last minute. I went sailing over his head, my hat fell off
and I bashed into the fence and the ground. Sal stood there while I was fighting the urge to either throw up or pass out, and looked at me as if to say "what on earth are you doing down there??" Cheeky little beggar!
My RI has taught me a new technique to try if he does it again, but I don't think we'll be cantering for a while! That totally knocked my confidence. What you do is dig your left rein into your horses shoulder and cross your other hand over the top, so that the reins cross behind the withers. Your horse ends up pulling against himself and will eventually stop. I don't know how painful this must be for the horse, but I suppose far more damage could be done to both horse and rider if you end up totally out of control.