Thank you for all your input! Here's the plan for now:
1) General fitness. I used to be in incredibly good shape, but the past couple semesters have been dreadfully busy, and I let it slide. To remedy this, I'm trying to incorporate more activity into my routine. For example, I have a few free minutes in the morning, so I'm doing cruches and pilates before getting breakfast started. I'm trying to walk my dogs at least a half hour a day, which is good for me and them. I'll look for other ways to add to this.
2) Reading. It's been a long, long time since I had regular lessons, so I need reminders of how I'm supposed to ride.
3) The riding buddy is a good idea, but it's hard to find someone who rides at the same time I do and my schedule isn't flexible enough to change right now. I can probably find someone to swap lunge lessons with or something like that. It's not so much that we'd teach each other as just have another set of eyes on the ground, keeping the horse going forward. Izzy wouldn't be much good for this, but Flash or Cassie could do it.
4) I'll just say it now. I'm terrified of seeing myself on video. I don't like the sound of my voice recorded and I don't like to see what I look like. I think it's a lot worse since I've put on weight, too. This is something we can work towards, but I'm not ready for it yet. (And yes, I hear the argument that if I do it now I'll be able to see how far I've come, but some things are best forgotten.)
Now that I'm aware of the magnitude of the problem, I think I can make strides to fix it. As Kate mentioned, I need to realize what I'm doing and how it affects (effects? I can never keep those two straight) Izzy and any other horse I ride.
And now, back to the homework that's kept me away from Miss Izzy the past several days. :-(
5) As the weather gets worse, I do traditionally ride bareback. I have ridden Izzy bareback a couple times, and she's ok with it, so we will move on to that when it's too cold to do much else. In the mean time, we'll work as hard as we can with a saddle.
PS Bear with me on the header. I'm trying to change the picture, but it's more complicated than I thought.