Dressage is hard

John rode Duke yesterday, and it took me quite a while to get all the moving parts (of me) to coordinate enough to ride him myself.  For a while, I thought it wasn't going to happen, but John persevered, and we made it.
First, I got to watch Andrea, Allison, and Sarah's jump lesson, after I took Duke up and down the hill in the sun.  It was really interesting to watch both their flat and their jump exercises, the differences and similarities between the three of them, and then which questions they asked John.
We started on a circle, John had me get Duke more round.  He said Duke was pretty stiff yesterday too, which even I could feel when we jumped Saturday.
Then we went to a 10 meter circle around him, counterbent until his inside shoulder moved in, then he could bend back to the inside.  John had us canter, and then - horrors - sit the trot.
At both the sitting trot and the canter, I had trouble keeping my damn butt in the saddle without curling up my heels and hunching over my shoulders.  Especially when I was riding with my reins short and out in front of me.
I had to really think about pushing my butt down, pulling my shoulders back, and then pushing my heels down.  And then checking that my left hand hadn't dropped.  And by the time I used all that brain power on myself, I had to start checking again.  I couldn't just feel and react to what Duke was doing.  And when John would have me do an aid, it was like the whole house of cards collapsed.
So Duke eventually got softer (I don't understand why), but like John said, at first it was like riding a jackhammer.  We did 10 meter circles at the trot, changes of direction, and 10 meter circles at the canter.  A lot of it was asking him to bend, but we also made the circles smaller and larger by pushing his front legs over the top of each other and leg yielding back out without giving away the reins.  At the sitting trot, John said to think about legs on/off/on/off to help some with the sitting, but it really felt like it was just my lower back that was stiff and wouldn't yield to let me "bounce" the trot.
There were so many aids, I couldn't think fast enough, especially when I needed to react or when one hand (or leg) needed to be doing something than the other hand.  It was really good practice, but my god, how many hours is it going to take before I can do this stuff "naturally"?