Based on ill-remembered citations of the efficacy of exercise for improving focus and general mental health, and after a lot of angst about body acceptance, I I reduced trivial inconveniences to working out below the inertia setpoint and started jogging three days a week. (I settled on running after an extended period of never getting around to signing up for hot yoga, crossfit, or a membership to the Y so I could swim, all of which seem more appealing.)

Good outcomes so far: feeling of accomplishment post-workout; feeling of accomplishment when I put on shoes and leave the house (remembering that not long ago I was basically incapable of making myself do anything I found unsavory); getting a lot less winded by minor physical exertion (e.g. walking briskly up a hill or flight of stairs). Meta-good-outcome: practice at finding and focusing on successes for self-motivation.

Waiting for more data: My focus has not yet improved discernibly. To do: self-test whether focus improves globally if I focus on jogging while I'm doing it.