Ride the Sky - I think that's really good advice and worth a shot. I don't know what his deal is with the barn because he doesn't even actually LIVE in the barn - he stays in an outdoor paddock with a shed all the time. :roll:
It was a lot better today - horse did NOT want to be collected from his paddock and wanted to play a bunch of games with me in ankle-deep mud, and I thought "Oh, no..." But he only pulled one of his tricks, and it was the race-to-the-barn and poke-away-from-it.
My teacher has told me 1,000 times that I need to be one step ahead of him, but FINALLY that part of it came together. Playing catch-up and correction was causing TONS of problems - I was always either trying to fix the pace, fix my balance, and fix the diagonal (which I came off of while fixing the pace or my balance).
All of a sudden, it clicked and I realized "OH! I can't wait for him to monkey with the pace, I need to be delivering the unambiguous signal to keep the pace steady BEFORE he speeds up or slows down". So then I would just post slower and a little more heavily before I got to the place where he wants to gun it, and I'd lay on some leg and heel before I got to the place where he wants to slow down.
It worked like magic. Suddenly we had a consistent pace (well, more consistent, at least) and he fell into line. So, it's clear: he did this because he COULD. Once I got a step ahead of him, the monkey business came to a stop. We were Trotting Fools for the next 10 minutes.
(It did help a LOT that he wasn't, well, horsing around as much, too...so a combo bad rider/bad mount day on Monday).