Okay, so last year I had to put my horse down because he broke a bone in his knee (RIP). Since we could not afford another horse my mom let me ride hers. I had ridden him before, but that was a long time ago. So she tore her ACL ligament in the back of her knee and couldn't really ride. Now that her knee is getting better she wants to ride every time that I do. The thing is that she hasn't ridden in a very long time and is very unbalanced and after she rides when I get back on he is all stiff and very hard to ride. The thing is that I have brought him up to a higher level than she is. I don't really like it when she rides but I don't want to tell her no because it is her horse that I'm riding... What should I do?