Okay. Then here is plan B. When he becomes perfect at the ground work, then of course you will practice this while you are in the saddle. Gently apply pressure to the left rein toward your knee. When he gives, you will release. When you have perfected this, you will take it with you into the arena. Start by walking, ask him to stop, take three steps back, and then ask him for his head. Then move up to the trot. If you feel him speed up, you will ask him to stop, take three steps back, again stop, and apply pressure toward your knee. Then proceed. Work your way up to the canter. He’ll figure out that speeding is too much work, and this should help you gain control again. It will also prevent you from becoming scared, and “choking him”, which is a natural response to your fear. I hope this will help you. Please keep me posted.