I don't know how great a proportion it contributed to yesterday being a really good day (the rest of the week was miserable), but I got a full night of uninterrupted sleep Friday night. I was woken up twice a night during the two nights before that. This may have worked.
Other possibly contributing factors: 1) It was sunny yesterday and 2) It was Saturday.
Speaking of not-completely resolved mysteries, I woke up with what felt like heartburn on Christmas Eve. By the afternoon, it seemed as though a part of my abdomen was sensitive to the touch, and getting up and sitting down triggered the pain.
On Christmas, it was less sensitive to motion, but it still hurt if I dragged my hand across the area. I called the nurse line, which suggested I go in to be seen in person. I decided to wait for the next day.
The next day, the PA checked a bunch of things. She said that the sensitive area does correspond with a muscle, and it could be some kind of muscle tear or strain. She said it was possible that moving the skin over a sensitive muscle could trigger pain. But she did rule out shingles, which is preceded by skin sensitivity.
By Friday, it was completely gone. I will probably never know exactly what it was!