Somebody mentioned martial arts as a way to learn how to fall properly, and they may be right. I know I learned how to fall without getting seriously hurt by playing soccer. After a while, it gets instinctive and you don't even need to think about it. Heck, I remember a crash where I was focusing more on twisting my bike with my feet to land drivetrain side up as it was flying over my head than on how I was going to to land. I hit the ground, rolled to a stop, then jumped up to pick gravel out of my skin and look for damage.