I spend most Saturday nights at home in yoga pants, rereading favorite novels or watching old movies, or playing Monopoly Junior with my seven-year-old. (If you think Monopoly is boring, then you haven't tried Monopoly Junior.)
This way of spending my Saturday nights makes me happy. If you went back and told my cooler 20-year-old self about the typical evening that awaits the future her, though, she would be pretty devastated that her life turns out to be so ... boring. That a Saturday night spent reading a book -- not even a new book -- qualifies as a great time.