A struggle-eureka jump lesson

Today's lesson was frustrating, insightful, and interesting.  The interesting part was I got to share it with Katy, and she was having to really ride, and it was interesting and useful to watch how she handled the horse and stayed balanced and calm.
The frustrating part was I - over and over and over again - would get the distance wrong and so slip my reins so I wouldn't grab Duke in the mouth, which would then just snowball because I couldn't get them back in time.  Until John said "here's what you do instead" and then it was a lightbulb/eureka moment because after I did what he said, it instantly fixed the problem.  It's frustrating because why do I keep making the same damn mistake until he has to step in, why can't I just try something different myself and show some initiative?
What needed to be fixed was balancing Duke further out and away from the jump (usually with a half halt with the outside rein).  If I balanced him a few strides out (or, in the turn heading towards the jump, which was a few strides out), we would come to the jump on the correct distance.  Then he wouldn't have to stretch to get over the fence, so then I wouldn't have to slip my reins, so then we would stay put together to keep going.
What we were doing was the long four stride line, then a right hand turn 270 degrees around to go over the red oxer, then another right hand turn 270 degrees to go over and black and white oxer, then a four stride (?) bending line to a vertical with a plank.  A tiny handful of times, we got it just right.  Most of the time, the turn from the red oxer to the black oxer flummoxed me (I also wasn't turning my head around soon enough, because I was looking at the wall past the red oxer sure that this would be the time we wouldn't make the turn), and so we would drift left.
Duke felt a little short and like he didn't have as much power today.  The fences felt big, and I felt like we weren't coming up to them with enough power, but if I kicked him, he got long and flat and it felt worse and made the distances in between the fences wrong.
So it was a great reward to get the half halt before the fence and see just how much it helped Duke get over the fence.
The other big insight was, the first time through the oxer/vertical bending line, I just sat there like a bump on a log and waited for Duke to figure it out.  John said that I've got to help him, and rebalance him, and so after that, it went a lot better.
John likes that Duke tries to get over the fence, even if the distance is wrong.  He's very forgiving and honest.
I also asked John about the show (jump) questions.
We raised my stirrups a hole after he watched me trot and then trot without stirrups.  He said we talked about this a few weeks ago but decided not to do it then.
He said that we won't decide on the Rebecca classic until we see how he goes at another show or two, to see if his first show he was just backing off.  So we'll see how he is at EI next weekend and see if that helps.
I told him that I had to hit Duke with the stick (for the first time ever) on the first fence on cross country, and he said that first fence was hard because you not only had to come out of a bending line to it, but the horses were looking back at the horses in warm up and not really paying attention.  So it was the right thing to do.
Duke rubbed the tables a little, and John said that is good for an eventer; that they jump long and flat and graze the fences, and that helps them make the speed.  He said Anna had a horse that jumped up and over every fence, and to make time, she'd have to go 600 mpm in between the fences because of the time she lost while her horse was up in the air over the fence (actually, at 2 seconds per fence, for 20 fences, that's 40 seconds!).
Duke spooking at the lunge arena and ribbon; John said that he doesn't have kids hand out the ribbons, and tucks them under his arm so he doesn't spook the horses.  He said a lot of people sneak out of the victory gallop, especially at the upper levels, because the horses are just too hot and conditioned by that point.  He said somebody got bucked off in the victory gallop in his class.
He also said that the thoroughbreds tend to be quiet the first time they're at a place (it's new) and then a little more of a handful the second time (it's not new).  He said I'm not ruining his ground manners with the shit with the bridle.
I asked him about Brooke's comment that to be ready to ride prelim you need to be 80% accurate.  He said his opinion is that it is more about your reaction time and accuracy.  Training level is 5 seconds; advanced is 0 seconds.  He said it's why A struggles at advanced but can do intermediate - she can make a decision and correct in the 1/2 second, but needs to be a little faster at advanced.  That is ominous, since I have terrible slow reaction time.  On the other hand, I think I said this a couple months ago, I noticed that I have "more" time when I'm jumping now than I used to, and I think that's some things becoming rote and also - hopefully - maybe a little faster reaction time.