You need to work on your center of gravity, and to work it on the ground, with unstable elements like a 'bosu'.
You work step by step, to try to be always lighter in the saddle.
I am also a physical trainer for riders, the @ffe calls me to work with French team jumping, dressage and vaulting riders.
We mainly try to teach them proprioception exercises, to try to release the horse's mouth, and to be balanced.
Whatever happens under us, we need to have our pelvis, shoulders, and heels aligned. And in vaulting, it's our specificity, when we are standing on a horse, we need to be able to balance ourselves in the best way.