I LOVED the writing; and I'm so glad you're okay! I totally know that feeling of "Oh s***...but this is so fun I don't want to stop", haha.
Image isn't a bolter; more of a "stop and drop", but I used to gallop him when I kept him on my mom's farm. He's usually a bit on the lazy side (unless he's jumping), but he would get SO excited from galloping back and forth around buckets (I didn't have barrels, haha) he would get all snorting and blowing and prancing all over the place. It wasn't scary, though because I knew I had complete control over him.
I can't imagine what it's like to be on a galloping horse that you have NO control of! Good job staying on =]