Some people take too many liberties when it comes to work. We all have different definitions of it, I suppose, but it boils down to being paid for services. You provide a service, and you are compensated monetarily. This is sort of the barest bones definition, but it bears repeating because bosses don’t always understand that. Sometimes they only hear the first part, the «provide a service» part, and they forget about the rest. 

Because no matter how much you love your job, unless it’s literally a volunteer position, the odds that you would do it for no money are probably slim. We all have lives outside of the things we do to make money, and we’d like time to live them. So it’s healthy to draw boundaries around your work life when you can– not that this is an easy thing to do. They don’t always make it easy.