its because you learn to fall. have you ever watched an experienced person and someone who is learning fall in the same way? the best example i can come up with is wakeboarding watching someone who is learning and someone who knows whats up, they both caught their front edge over the course of the day, the person who was learning got mad whiplash and was like "fuck it i quit wakeboarding" and the experienced rider just got back up and went at it some more. experienced riders know how to react based on how they are falling, and what to expect based on what they are attempting or doing.