when you say "motoring", do you mean that you pump your whole body in the canter??? (leaning forward and pumping your upper body with the horse?) If so, I've seen people do this a LOT(including myself)....try to focus on your upper body being still and balanced, with your lower body doing the moving. I find that pulling your shoulders up above your hip will mostly keep this from happening. Easier said than done though!
A horse is the projection of peoples' views about themselves--strong, powerful, beautiful--and it has the capability of giving us escape from our mundane existance.