Yup, I get this a lot. It's strange, because I love my subject more than I ever imagined I would, and I've done some really awesome things since I've started. However, I have so few friends within the university itself and spend most of my time feeling lonely, so I can hardly regard it as a positive experience. I don't think I went at the right time in life - should have taken a gap year and grown up a little before I did. Still, two more years and with any luck I'll come out with a decent degree and then move on with my life.
(And it's nothing to do with joining societies - I've been a member of almost 10 this year, and have exec roles in two next year. I've just failed to form any close friendships through them)