Does anyone really know why bouncing takes place? it might help to understand the reason to fix the problem?

My opinion is that during the trot the horse is doing ups and downs movement, and hence, it's very logic that anything on its back will bounce, lifting it up then dropping it down.

If this is true, and no one is recommending to squeeze with any muscle to stay fixed on the saddle? so howcome this bouncing can disappear?

i.e what can singing or breathing do to some physics rule ? every action has a reaction, trot = anything on the back will bounce.

Let me know if i am getting it wrong all the way though