Not being able to take a “mental health” day off, in both high school and college. In high school my parents wouldn’t let me (though I don’t fault them for that), and in college it was hard to keep up if I even missed one lecture. As an adult with a job , if I need a day to decompress, I can decide to take off tomorrow and nobody can tell me no. In school it was hard to keep on going with the tank on empty.