First of all I am going to say - reading your post was like reading an excerpt of my own life. I have just recently gone through nearly the exact same thing. I'm going to tell you my story and hopefully you can draw some conclusions out of it. :)
When I was 14 my parents bought me my first horse. An 8 year old OTTB that I had been taking lessons on. At the time, I loved him. He was so calm and such a good boy. About 3 months after we bought him, I was riding him in our outdoor and out of nowhere he bolted and ran full gallop around our outdoor completely out of control. I stayed on for about 10 laps and then I fell off. I assumed he had been stung/bit by something.
A few months later he started bucking, we assumed it was because he wasn't getting as much turn out as usual and so we started lunging him before riding. He bucked me off a few times throughout the next few months, and gradually I become more and more scared to ride him. In January 2005 we moved him to a new barn - a really big, really nice barn. The only problem with it was that they didn't have any fields, just individual paddocks. So, of course, we planned to continue to lunge him before any riding. On the morning of what was supposed to be my very first lesson on him since we moved him, I woke up with a terrible feeling in my stomach. I told my mom I didn't want to ride and she called my coach. My coach agreed that she would ride him, but my mom wanted me to go watch at least, so we went. My coach tacked him up, lunged him, and hopped on. He was being very good, but suddenly he bucked. She fell off and broke her collarbone. From that point on I couldn't ride him any more than walk/trot for about 10 minutes and it was like pulling teeth just to get me to go there. I had completely lost confidence.
We gave that horse away and I decided to try riding at a more casual/fun barn. I rode there for around a year, and I was fine with riding the school horses but if I was ever put on a hot horse, I would simply sit on it. Couldn't bring myself to do anything.
Finally I realized that I was learning nothing at this barn. My first barn had been a very strict dressage barn, this one was a very casual eventing barn with TONS of little kids running around all the time - they were more a "family fun" type of place than a serious lesson barn. So, I decided to go back to my first barn. I rode there for maybe a year or so, and again I was fine most of the time, but if a horse was acting up or a little hot I would completely just melt down.
In Spring 2007, I had to stop riding. I was in Grade 10 and needed to keep up with my work, I had a job, my parents no longer wanted to pay for my lessons and if I wanted to pay for them I'd have to work way more which wouldn't leave me any time to actually ride. I ended up spending two years without sitting on a horse. To this day, I still have no idea how all that time passed. Suddenly I just realized, "Wow, it's been two years." I immediately started looking for leases and horses to ride. I jumped around between horses to lease but they never worked out - one was sold, one was moved, another one was going to be listed for sale. But at least I was around horses, and enjoying myself around them.
During that two years where I didn't ride, I grew up. Now I look back and say "Why couldn't I have just helped him work through his problems?" Even though I know that then, I just could not do it. I was terrified.
Now, just a few weeks ago I bought my first horse since. A 3 year old OTTB. But you know what? I am passed being scared. I know now that I can be confident in myself as a rider/handler because I have so many years of experience. I still get a little worried if anything starts to go wrong, but now I take a deep breathe and I think to myself, "what is actually going on here?" and I realize that, my horse is not acting up to hurt me - he's upset at mosquitoes (true story, my horse is such a wuss when it comes to bugs), or he doesn't want to leave his herd behind - but I am willing to work on it, instead of just retreating because I am scared.
I hope my rambling along has given you something, if not just a good story for a few minutes.