As a dressage instructor, I have to help my students understand many, many topics in order to develop their and their mount's dressage potential. One thing I often need to help students understand just how active they need to be when riding dressage. Between the half halt, the posture, the bending aids, the movements, the balance,the steering, etc., there's a lot going on up there. Often, the aids are small, so they aren't obvious from the ground. When I introduce this concept, usually I will hear something along the lines of "riders look so quiet up there, like they aren't doing anything."
To which I reply, "There in only one horse that I have ever ridden that I didn’t have to actively help with his balance. One horse, and only one horse, that I could just sit up there and do nothing and he would maintain perfect self carriage. That horse lives outside of Wal-Mart. The best part is he only costs fifty cents to ride."
So one of my students sent me this photo. His balance is a bit on the forehand for my taste, but heck, he is in perfect self carriage.