The Seat

When I was a kid I rode dressage for a few years (very intensely). Anyway, starting again as an adult has really opened my eyes to a lot of things I didn't grasp back then. Like the seat aids. I knew it was vital, I got the concept for the most part, but I completely failed with the subtleties of it. I thought the "seat" was the thighs and seat bones. To turn -> thighs and one seat bone; To stop -> thighs; To collect -> thighs and calves and reins; I had thighs of steel. At my last lesson I was struggling with controlling Ava's forward momentum at the canter. I tried bouncing the reins, and it half-heartedly worked, but I had to really bounce to get a response (which I'm not a fan of doing). So I whined to my trainer, who gave me a "you should know this" look, then set about explaining how to influence Ava's momentum with my hips, abs, shoulder's, and calves (I'm sure she's explained this all before, but I frequently forge...