Amazing dressage lesson

This morning Duke and I had the most amazing dressage lesson.  John did a couple of unusual things; he videoed and showed it to me to show me what he was seeing, and then he also walked alongside Duke and showed me the aid.  Then he did a normal thing, which was tell me each change, but this time I had a bit of a eureka and got it better than the last few attempts he's made.
First we rode our Novice test, which was a bit lousy.  So then he had us work on a 20 meter circle.  The first thing we did was work on the proper shape and size of the circle.  He stood on one corner, made a mark in the footing on the other corner, and then I had the two letters of the arena to use.  My circles went from weird elipses to round circles, which helped Duke maintain the bend in his body.
But then we worked on the bend.  Hard.
So first - John said to pinch the rein between my first finger and thumb, but then I can use the rest of my hand to squeeze/release; instead of using my whole hand to pinch.  That's something that no one has ever told me, and was definitely a light bulb moment.
Then he showed me how easy it is to move Duke over by using his finger, but he said I need to give sharp, quick aids, not cling on.  He hasn't had to tell me that in a long time, but I remember months and months of trying to catch onto it with Charlie, and with Duke, he reacted immediately.
We did 20 meters, got Duke round, then did 10 meters, then did 20 meters again keeping the same bend as in the 10 meter.
To get Duke to bend around his body, there is a bit of art.  He is so "narrow" (short backed is what I would call it), that he can dart all around.  And if I get one part of him bent, he just moves another part.  So it is aid-aid-aid-aid-aid-breathe-aid-aid-aid all the way around the circle.  For now.  For example, if I use my outside leg to put his haunches into the circle, then he tries to bend his neck to the outside.  If I bend him back to the inside through his neck, he'll either pop his outside shoulder out of the circle, or move the haunches back out.
What I had to do was feel where his shoulders were, and then think of how I wanted his body aligned.  Maybe 5-10 times, I could feel it and started the aid just before John said it, but approximately 2000 times John had to say it.  (I was inordinately proud of the 5-10 times, then we switched directions and my success rate of .05% went back down to .00%).
In the trot, I use my outside leg (up closer to the girth than I "like" for it to hang, but not jammed in front of me either.  John had to show me, and to wrap it down and around Duke, I kind of open my knee.  It is a little further forward than feels right, but not as far forward as I try to put it when left to my own devices) to keep his outside shoulder from popping out.
But in the canter, I use a half halt.
Basically, to get around a circle, I have to use inside leg to keep him from falling in, then outside leg to keep him from falling out, then both legs to push him forward, then some inside rein to bend him again, then outside leg to keep him from falling out, etc.  But when all the pieces fall into place, angels sing and all is well in the world.  We could do it; we just needed John's help to get there.
John said that because Duke is so narrow (short front to back), if I put my leg back where it likes to hang, it is several ribs further back than it was on Charlie.  And it pushes his haunches in and he has to compensate.  I have to think of him like a little speed boat who needs lots of little corrections to stay on track; Charlie was a big cruise liner who you had to start bending way ahead of time and wait for it, and who you had plenty of time to feel the drift coming and correct it; Duke I have to be right on top of each moment and ready to ride it.
What is nice about Duke is that he is responsive and sweet, so when I give the aid, he immediately responds (or at least I think he does), and it rewards me for doing it right.
It was an amazing ride.  It made me feel really hopeful about the team that Duke and I will be, and hopeful that I'm not the world's biggest fuck up of a rider, and am capable of learning.  And it makes me suspect that John is the world's best trainer, and that he did this sort of building confidence ride before his show on purpose.  He's always been excellent at progressing the lesson so that you end up doing something you never would have imagined doing at the beginning.  Once again, I wish I could ride with him every day and had been riding with him the last 25 years.