Took me awhile to catch up on back posts here ... interesting discussion about fear of getting hurt and fear of "not being good enough". I have a couple of thoughts although nothing very original.
I have long -- long-- thought that competition is way overdone in our society, and that on balance it is far more destructive than it is positive. There is a big segment of horse people who for whatever reason have come up believing that competition is the only way to be a 'real' horse person. Their first exposure to horses was in a lesson barn where the aim was to produce competitive riders, and they never really experienced any other facet of riding to any great degree. I believe you see this more in English styles, as there has always been a big population of western riders whose sole aim is trail riding.
I probably feel so negatively about competition because I don't enjoy it. Even when I win, there's so much stress involved it never seems worth it. So I have this jaundiced view going in. I see how horribly horses are often treated in the service of prizes, and it turns me off even more.
Fearing getting hurt seems a function of two separate things. One is not riding as a child, and the other is surviving a bad fall. I can't imagine getting on a sproingy horse like mine and casually heading off alone down a steep rocky trail if I had not spent a sizeable chunk of my childhood doing exactly that. Even now, when I first swing up after a long hiatus I always have this moment of "hey, there's nothing to hold on to up here!" Then it goes away. But for all the times my horses have dumped me, I have never gotten terribly hurt. I don't know how I would react to that.
I also lose my temper pretty regularly. Oh, that is a part of my personality I wish I didn't have. Seems like the main reason I get angry is because I have expectations. No expectations, no temper! Nothing I do out of anger is ever a good thing.
I have a tip for Hugh, though. When you see a truck coming down the road, have him sit and look at you for a treat. I say "watch me! watch me!" Keep little pieces of cheese or something with you (trainers use waist belt "bait bags"). This works for most dogs. Dogs think: ack, scary truck, alarm alarm! Hey, I scared it off! Woo, I'm gonna do that next time too! You have to interrupt that thought process. Preferably well before he starts barking and pulling. Take advantage of being able to see farther down the road than he can, and get him staring up greedily at your pocket before vehicles pass.