i have issues with loosing my stirrups at the canter and sometimes jumping because i dont distribute my weight evenly in my legs/heels always so then my heels will just ride up a little... well actully my whole leg rides up trying to squeeze my horsayy generally and oops there goes my stirrups, but ive gotten better. No stirrups helps, like pony hunter said, riding a diffucult horse/pony ALWAYS teaches you (wether they just do little things like dip there shoulder out or buck) devine and sadie gave you good ideas and info that will most def. help.. you can also try laps of jump position @ trot and canter, vertical far at the trot or canter; touching your toes, to jump position to vertical far and back down to touching your toes ect (tie your reigns in a knot, and this is really good if your horse goes on auto pilot or at least moves off your leg, it will help you to learn to steer without reigns... like using ur legs like u should, and also heels dopwn and def balance) at the trot, im not sure how well that would go at the canter unless your REALLY talented or on a REALLY REEALLY good horse, but any of those things really help. You may just need to build up your lower leg and work on flexing your heels... but im sure bob and theres lots of people there that if you ask to help you, they will. Im sure youll get it =)