Answer

By Your Horse

Natural Horsemanship Expert Charles Wilson says:

This year your young horse is nearly at his full strength, but his muscles are still developing. One of your main focuses should be the muscles that carry the rider.
You should also be getting him to mentally accept the rider’s wishes with increasing willingness. Do lots of exercises that encourage him to accept the rider’s aids of thought, body, legs and hands.
Work both in and out of the arena – the outside world is, after all, the best school for a young horse. Ideally no more than 25 per cent of your time should be spent in the formal classroom of the riding school. This won’t be possible for many, but you must make your time together as interesting and stimulating as possible.