I am not one to refuse a soapbox to stand on, so here I present my final half-assed attempt at dispensing advice and farewells. I'll try to keep it quick. If you refuse to have fun now, think of how stupid you're going to look trying to make up for it in your late 60s. Go to the park when you can, and walk barefoot in the grass. Smile at children and the elderly, no matter how deranged they seem.
Eye contact is an anti-depressant.
Don't dress just like all of your friends. What else when you see people you remember from freshman year, don't just assume they wouldn't remember you if you said hello. Have as many snowball fights as the winter will allow. Don't take a class just because you heard it was easy, try something you wanna learn about. Check out the Carnegie Museum because it's free and good-looking, intelligent people hang out there.