A couple of people have mentioned the fear of falling whilst standing, and a few replies have been to treat it as part of riding (the falling, not the fear.)
I have spent most my adult life practicing Aikido, which I found really handy when I got back into trials (which, btw, is the best bit of advice that's been on this thread ~ Get a trials bike and live on it for a year)
The first thing I was taught all those years ago was how to fall without hurting myself. How to roll etc.
But more importantly to think about falling, for it to be a continuation of the action your performing (in this case riding)
I don't mean plan or decide how to fall as it happens.
There wouldn't be time at full speed, although when trials riding you are quite often stood still during or just after a move, and can actually decide where to go if you can't get your balance back.
No, I mean in the same way that a a novice road rider might panic if the back wheel stepped out and an experienced off roader is almost always in a controlled drift, regard falling (or tumbling
) as part of the whole process and your reaction changes from "Oh s**t to "Lol, here we go again"