Someday in the hopefully not too distant future, you'll develop a little voice in your head that says, "sit back!!" It is the global saying of any instructor in the world about any rider who suddenly finds herself on an out of control horse. If you go to any show and you see a horse take off, you'll hear 20 people (all instructors) yell in harmony, "sit back!!" It's pretty funny actually. Anytime I get into a sticky spot with my horse, I always here them on my head and it goes a long way toward helping me stay calm, sit back as advised, and regain control.
Next time you feel out of control, just remember, there are no penalties for stopping. Just sit back, bring your horse back to a trot or even walk if you need, re-group and try again. Besides, once the canter finally clicks for you, you'll absolutely love it. It's a fantastic gait.
You just have to see your distance...you don't have to like it.