When I get to roll over and go back to sleep if I'm still tired, even if it's noon or 1pm or something. If I'm visiting my parents (or someone is visiting me), I have to get up early so that I can actually, you know, visit. If I have school or work, I have to get up early for it and even on weekends I can't let myself stray off my sleep schedule too much, even if I didn't get enough sleep for whatever reason.
This summer I've had no obligations and the most satisfying thing has been not having to worry about going back to sleep if I want to. I do still feel a little guilty about it sometimes though, haha.