Bit interested in hearing your stories, when your on a horse and you've hit the "OH CRAP" stage.
I've done this twice, both times on my 16.3 OTTB, Sonnet. I'm 5'2'' and 105 lbs so when he wants to get his way, it's REALLY difficult to stop him sometimes! (he used to be really nervous)
The first time was about a year after I bought him. He was acting really weird in the arena, as if he couldn't focus. I kept telling my trainer that he was going to run in to something. To this she replied: "Only an idiot horse would run in to something!" Well… thirty seconds later, as we were cantering on a 20 meter circle, he started drifting to the outside. I pushed him in with my leg and tried pulling on my inside rein because he wasn't drifting just a little bit, he was drifting a lot!! He ran chest first in to a standard. As he ran in to it, I jumped off, landed on my butt, got up, and grabbed him to make sure he was okay. It happened so fast!
The second time, I had Sonnet on the track after working him for a long time. He is usually great on the track, very laid back and easy. I guess his racing instincts caught up with him because while we were cantering, he broke in to a gallop with me. It was fun at first because I felt as if I was in control, and he was having fun, but then he started heaving his head under and I lost control. I tried circling him, no use! I tried pulling back with all of my force, didn't work! I tried sitting and giving him all the rein, nope! So I figured that he might just run until he stops - okay! UNTIL HE DIDN'T GO AROUND THE BEND OF THE TRACK! He was headed right for the barn. I tried to do an emergency dismount but he was running so fast that I couldn't get off, I was literally sticking to him with no stirrups, one leg half kicked over his butt. When I eventually pushed myself off of him, I landed on the asphalt of the barn driveway - and he ran right through the barn! As soon as he realized I wasn't on his back, he turned around and trotted back.
We've never had such incidents again!! And thank goodness for that!!