Join Date: Jul 2008
Location: Higgins, TX. YeeHaw!!
From that last picture, it looks like you are bracing against the stirrups with your feet and what I can see in the video pretty much confirms it, IMHO. You put all your weight on your feet and that causes you to lose your seat and come up out of the saddle like you are doing at the lope. It also causes you center of gravity to be off and that's one of the reasons why your hips and upper body are all over the place.
It takes a long time, a lot of repetition, and constant awareness of what your body is doing to re-train that muscle memory. Believe me, I know, I still fight with that exact same problem sometimes because I spent years riding with most my weight on my feet instead of my butt where it should have been. If your horse is nice enough, some no-stirrup work would likely help you quite a bit, though that's hard to do in western saddles.
Always remember that feeling of looking at a big, open country over the ears of a good horse, seeing a new trail unwind ahead of you, and that ever-spectacular view from the top of the ridge!!! Follow my training blog: http://robertsontraining.blogspot.com/