I think the answer will differ wildly for different people. What I wish I had done: - Pay at least a little attention to nutrition. - Be more willing to do th

I think the answer will differ wildly for different people. What I wish I had done: - Pay at least a little attention to nutrition. - Be more willing to do things by myself; there were certain activities, for which I had a vague impression you were supposed to wait until other people invited you to go with them. - Be less afraid of upsetting professors and other authority figures. (And I say this as someone who is a professor now!) - Try less hard to weasel my way into the "in" crowd. (And by "less hard" I don't mean "not at all"; these efforts were worthwhile to some extent.) Conversely, there were all sorts of interesting people who weren't "popular"; try to make friends with them, or even ask them out on dates. - Somehow found a way to relax more, although that is always much easier said than done.