One interesting thing about living alone is that there's nobody around to point out unhealthy decisions. I realized recently, for example, that nobody was going to make me stop eating Spam and Lucky Charms. Personal health is a new sort of responsibility.
I had a bit of mild neck pain the other day-- maybe I have bad posture or my backpack is too heavy. I had bad posture and a heavy backpack in highschool, too, but back then I used to watch a lot of tennis so everything worked out.