The fact that I'm having trouble coming up with examples of self-care is probably a bad sign.

(Well, I can think of one: I should book a massage soon, since that's one of the things I've been doing less often than I used to.)

I'm doing generally okay at the sort of maintenance stuff lilysea mentions, mostly because of external prompting through OmniFocus repeating tasks.

Getting my obligate-extrovert social time is also a big help, often through conventions but with a smaller "maintenance dose" from the weekly game night at work.