Amazing dressage lesson

Today was a great dressage lesson, where I felt a lot of what John's been teaching me start to really make sense.
We worked on not breaking the connection by bending my wrist or putting my elbow forward.  Duke responds much better when my elbow is "connected" to my hip, and I pull straight back with it, rather than curling my wrist.
We also worked on connection from the inside leg to the outside rein, and shifting from a "C" to the inside of the circle to renvers (a "C" to the outside of the circle).  We did this by riding 10 meter circles, changing directions, and then leg yielding - just a bit - out to make the circle bigger.
Duke was great.
I, however, need to work on my posture.  In both canter and in trot, I need to sit up - pull my shoulderblades back, and in the canter, put my seat down (sit - glide - sit - glide) and then let my knees go "long", which felt a little bit like pushing my legs forward just a bit.
This was one of the very intense "feel" lessons, where I felt the aids connect to get the result, but it is - once again - hard to describe.  I don't know if that's because it's about feelings, which don't translate well into words - or if it's because it's still just a little bit too new and I'm just grasping the concepts.
Either way, Duke felt great.  It feels like we've made so much progress in two years.