Good, but not good, dressage lesson

Today's dressage lesson was a little weird. Mike was really happy with some of it, and there were certainly moments of brilliance, but overall, I felt like I didn't really catch on technically to what we were doing, and like maybe I didn't have good enough understanding of the feel either, to repeat it. So we'll see what happens tomorrow when I try to do it by myself.
We started out on our transitions. (Also, within 5 minutes Mike had to tell me to put my heels down. And then he had to tell me at least 10 more times over the course of the 45 minute lesson. I HATE my heels.) From trot to canter, we have been increasingly slipping into this diving down thing, where Willig's nose goes towards the ground and I tilt forward - I usually bend in half a bit.
So Mike fixed that by watching us struggle for a while, then getting on himself, riding Willig for less than five minutes, putting me right back on him while it was fresh in Willig's head, and then doing it over and over until I got it right.
The interesting part was, while Mike was "poofing up" Willig's shoulder air bag (what makes him so delightful to ride after Mike has been on him, before I deflate him back down again), Willig did an ugly buck and donkey kick. Mike reacted near instantaneously, lifting both hands to lift Willig's head, and then smacking him with the whip. His reaction was so fast I had hardly processed what had happened, but the buck was quite impressive to see from the ground. No wonder he unseats me.
And it made me wonder - he's been naughty going on two months now. Maybe (probably wishful thinking) but maybe because he's having to work harder?
So, the steps for a correct transition up from trot to canter are:
Lean back; think firm core
Tickle with legs and hands
Ask with outside leg sliding up and back
And lift hands up
Do NOT let him rush forward or speed up
He should kind of "jump" up into the canter (it's very, very obvious when he does this)
And then immediately hold him there (thinking collected canter) rather than shove my hands forward and let him immediately nose dive
This work made Willig tired (although it also was hard for him to look at stuff and be spooky) and he got heavier and heavier and heavier in my hands.
When we got it right: sparkly brilliant.
But for the most part, I got it wrong. He'd pick up the wrong lead. He'd stumble a bit. He'd try to dive down. (That's not his fault, he's been diving for like 3 years now with me. Although he knows how to do it properly, I haven't been asking, so he needs to learn to do it proper now.)
Then, this sort of connected with the down transition (from canter to trot). I'd lift him up into my seat (I'd kind of squeeze with my leg and my inner thigh while kind of lifting with my hands, and his back kind of lifts up into my butt) 1-2-3 strides and then lean back just a bit for the down transition. A few of these were the floating ones that are easy to sit. For the most part, we'd go back to jarring around.
I let my reins go too loose (they are always sliding out) and so Mike said to stick between the 2nd and 3rd leather loop on the reins and hold it there. I think one reason why my hands felt "high" is because they're much further up on the reins than I'm used to.
And then we worked for a tiny bit on the sitting trot. I'm getting all stiff and bracing, and Mike was trying to get me to "bounce" on the ball on purpose, but this was really hard.
When we ended, he had us do the "impossible" 10 meter circle (from the jump lesson and the last lesson with him) and it was almost no big deal. A big difference from the last few lessons.
Mike says that I'm very close with the sitting trot, but we have let it slide a bit, and that I just need to "get" the movement. He had me watch J warming up for a bit, but all I can see is that she's pretty close to motionless but obviously doing something. (Just like whatever magic happens when Mike gets on Willig. I really, really, really want to learn how to make his shoulder balloons blow up.)