When I got Bunny she didn't know how to stop, stand, back up or slow down. (Of course she knew, but she wouldn't listen) I've had a very little progress just riding it out and doing endless circles/making her work when she sped up as I had been suggested many times. When I asked her to stop she would slow down for a few seconds at best, if I asked too much she would buck. If I asked for her to back up she would threaten to rear (I've never had her actually rear on me).
A few days ago I got really tired of it and decided I would work on it from the ground. For about a mile and half I had her walk beside me (no reins/lead or anything), trot when I said the word and sped up myself, and stop when I said whoa. By the end of the mile she would nearly be on her butt stopping as soon as I started to say the word. I also worked on her backing up at the touch of my hand.
What an incredible difference that exercise made under saddle! I can safely say we've had a breakthrough. I could transition from walk, trot, canter, stopping and backing up easily and with no resistance. It might sounds sappy but I was so happy I cried.