The way we sit on our horses needs to be checked every so often, however experienced or educated we are. Small bad habits creep in and need to be sorted out quickly.
When we sit on our horses squarely, some trainers suggest that we sit in a box made by or hand and hips. I think you should feel that you are sitting on a table so that the saddle feels flat, when your horse is carrying you correctly. You should feel centred in the middle of your horse, neither tipping in nor out.
As riders, we must check our posture is good. Holding our frames upright from our core muscles, so that the shoulders can relax and our legs hang down our horse’s sides. The shoulders should be upright with no hint of leaning back and the reins must be short with the hand going forward for every aid.
When we get a chance, it is interesting to have a lunge lesson. This helps with learning how to maintain our balance on a moving animal. We also learn to be able to use our aids independently of each other. All this leads to the development of a soft effective “seat”
Work on balancing your horse’s movement through transitions on a circle. Hold your outside rein steadily shut to maintain balance. Hold your core muscles firmly for a second to produce a half halt, and then ride 3 or 4 shorter higher steps, rebalance and then ride 3 or 4 longer steps. Work in the trot until you can really feel the difference. In canter 2 steps of shorter higher steps until it happens and then allow the horse to move forward again. As the balance improves add a few more steps. The natural progression is to then ask for your longer slightly lower steps in canter.