I cringe whenever I hear those ever-present riding school phrases when people are learning to trot or canter: -
"shorten the reins"
"sit up straight"
"heels down"
"kick harder"
(generally bellowed by a young instructor totally frustrated by the inability of those sweating pupils who just won't get it despite them trying their hardest!)
I promise you unless you are medically unsupple and stiff, you should be able to do a reasonable rising trot within 15 mins. If you have tried this and you can't, then what your instructor is telling you is putting you out of balance because he isn't teaching your body.
Not only does the secret lie in teaching your body but it also lies in teaching your horse (or the horse you are riding) to understand what you are saying. Most people who ride at British Riding Schools are sitting on horses that have no idea what a light delicate conversation with the reins and legs means. The horses are used to the banging and crashing that is the conventional way of riding and have just switched off. Imagine if a foreigner just kept shouting and kicking you and you had no means of escape. After initially trying, you'd soon shut down. But if someone helped you gently and kindly to understand their words you'd soon want to start that conversation with them. Even riding school horses can learn to trust. Horses roughly fall into two catagories - the forward going, rushy ones or the lazy ones. Using New French Classical methods, either sort can be the sweetest kindest horse ever!