I have been riding a pony at the stable I board at. He is not mine but the owner is letting me ride him. He is super well behaved on the ground, but when I am riding he can be super speedy! He is fine at the walk (i ride english) but when I am trotting I am constantly saying whoa and having to slow him down. Any tips on how I can make him stay at a nice controlled trot? I've tried giving and releasing with the reins, and posting slower then his trot, but no luck yet. Id like to be able to fix this without changing any of his tack.