Join Date: Mar 2009
Location: Central Iowa, USA
The major this I could see (which granted wasn't a whole lot, I hate critiquing videos, you just can't see much!) is you really grip with your calf and are not stable much at all in your lower leg which translates up into balance insecurities in your upper body. Think about instead of needing to grip onto your horse by wrapping your legs around him - trusting in your equipment! Your saddle is strapped on his back, as long as you're balanced in the saddle, you'll be balanced over your horse. If you can do that, you can bring your leg off slightly - pushing weight down through your legs and letting them stabilize and become independent to your horses movement (a tale-tell sign that your gripping is your toes pointing out and knees completely off the saddle).
Think about it similar to this - the focus of all seats of riding is to manipulate and guide our horses bodies in a way that is predetermined, whether it be going through a course of hunter fences or a barrel racing pattern. We expect the horses to take guidance from only touch and verbal commands, so our bodies must be strong and independent of their movement so we can choose when to engage a cue and when not to. If you are trying to grip onto your horse, you're not stable as a rider and thus not independent. :)
Work on becoming stronger and really solidifying your leg so you can then focus on your upper body. :)