Thanks for the advice. I'm not sure what to do except just try to pay as close attention as possible for the spooks. I've been riding for 20 years, and just never ever fall off. It hurts too much!
The two falls that I took -- one flat fall from about 6 feet up (he caught me changing my diagonal, so I think I was extra high) onto my back, the other mostly a slide off his hip -- really, really hurt. The good news was that, after the first one, I bought my first new helmet in 15 years (at the tack shop: "Is this helmet even RATED?!?"). I wonder if they sell padded riding pants? Or just a suit of armor?
Regular falling is too dangerous for my old(er) bones. I wonder if I should just do a lot of walk/trot/halt transitions for a week or so, to get used to my new weight balance. Both times I fell, it was only at the trot. So, of course, now I'm all tensed up which makes things even more difficult.