Summer camp got me started. I was trotting when everyone was supposed to walk in the first lesson, because my cousin who rode told me if you squeeze and cluck they'll go faster... and well, a walk wasn't fast enough for me. I was also the only beginner in that camp who had a jumping lesson at the end. I rode bareback, I was a daring little monster.
Then I moved to the farm where I am now, and got my gelding and got even more daring. :P
My highest point was probably getting 2nd, 3rd, and 4th places with Smokey in dressage at New England (A-rated) when he was 23 and I was 16, and neither of us had ever shown dressage before. My other high point, is happening right now, and that's training my filly.. but since she's not finished yet...
I don't really have too many low points, but I guess one would be riding for this tough instructor who really stripped me down to the bone and built me back up the year before I went to college. The other low would be everytime Scarlet set me back and made me feel like I couldn't do it. Now I know I can though, so it was all worth it.