basically if your thinking about getting hurt you will screw up. Really you shouldnt even think about anything, just loosen up and go with the flow. I got hurt really bad skateboarding a few years back. I was just doing a simple ollie over a small wall and onto a little ramp, it was a loading dock. Anyway I couldnt stick the landing, I would either bail out in the air and not even touch the deck after that or fall. I fell and kinda messed up my wrist, it really hurt and was swelling, but I had my mind set on making it happen. I tried a few more times with no luck, then I started thinking about how I just sprained my wrist and I could end up breaking it or something, but I went for it one more time with those thoughts in my mind. It was a clean ollie, textbook perfect, so perfect I thought I had the landing,but I didnt. My left foot landed just on the tip of the tail, and it proceeded to twist. I felt that imediatlly, more pain then Ive ever experienced. I had to practicle hop home on one leg for about a mile. When I finally pulled off my shoe and sock, my ankle had swollen into a softball. The next day I couldnt walk at all, still hurt like hell. Then my whole foot was bruised, all the way down to my toes. It was really jacked up. Doctor said I didnt break it but tore some ligaments, he told me it was worse then actually breaking it. After about a month I felt confident to get back on my board again, but I twisted my ankle two more times, not as bad though. It never healed back correctly.
I know this wasnt a bike story, but it sort of explains what will happen if your mind is not in the right place. Even now when I skate Im scared of gettin hurt. Im ok on a bike though.