After around 3 weeks of mostly bedrest either side of the Jan-Feb transition, I've been rebuilding strength via a daily dog-walking excursion with my parents. This has been 2km at about two-thirds pace, and seems to be exactly what my body can handle. The one time I pushed myself a bit harder my fatigue hit back, but still feels like progress.
Over the past few days I've even found a sleep routine that has me waking rested, rather than exhausted, without taking up my whole day (hopefully it'll persist!). This leads to both a better mood and some of the concentration needed to draw again, which I've been enjoying.