I was fairly fearless as a teenager too and when I got back into horses at 40 after a 12 yr. Break from them, I was still very confident. I was working with one of our 4 yr. Old geldings in a dressage lesson and when I asked for a canter, he tripped and fell on the first stride, taking me down with him. Rolled over my foot/leg and crushed my foot and ankle. I put the horse with a trainer to see if there were any issues. After I healed I took lessons again with the trainer and pretty much conquered my fear on that particular horse but now that my current colt is 4 yrs. Old and it's time to start learning to canter, I am freaked out! I feel like a chicken too but I just have these visions of him stumbling and going down and he's 18 hds. And much bigger than the other gelding! Sigh..... I am amazed at my fear, having never really had it before so I can totally understand what you are feeling. I'm going to have someone else canter my colt for me so I can watch and visually see that he will be fine. You might want to do that with your horse, just so you can see that he is safe and capable of jumping. Also, remember, you are riding for pleasure and if you aren't getting pleasure out of jumping, stop and do whatever it is that you love doing on horseback