I got ill with ME during college, which I started directly after high school, so not able to test how working might go.
However, I seem to have done a lot of stuff, of the things I did do. I went on very long hikes from a young age (9?). In the national forest or park, following a stream course usually.
I used to do school, and babysit, and volunteer for various things, and play casually at whatever sport was available to me at the time (I rarely had access to formal sports).
I did get a bit dizzy and see dark spots, after running a while. My friends thought this was weird so I believed it was unusual and I didn’t try to tell doctors.
I already had an uneasy relationship with doctors because I had stopped growing as a toddler. I remember them poking and fussing, and not figuring anything out. I started growing again (of course) but was always underweight (until I was an adult, then the underweight became a part-time thing). My parents made me eat all sorts of yukky health food.
I could do things like:
work all day setting up at a booksale, babysitting at the booksale or helping with the tables, then stay and help with cleanup (pretty sure that was 11-12 hours, but only 2 days in a row once a year, a bit different from a regular schedule);
do a full day of school and then cook dinner from scratch and clean up the kitchen (again, not every day, but in grades 11 and 12, I think I cooked or babysat most weekdays, then did my piano practice and volunteer work on weekends).
I still had time to read for fun and climb trees.
Like others, I did always need my sleep. I got up early, but I went to bed early, too. And when it was bedtime, didn’t much matter what was going on. I felt ill and generally went to bed.