I wasn't much of a school person, though I always enjoyed campus life and having friends around. But I must admit that there's at least one aspect of it that I miss tremendously: The End of the Year. Forgetting all the parties and fun and hanging out "one last time" for about a month and a half; there was that last little bit of time, where everyone's packing up, and you start thinking back over the last year and all that has happened - everything you've learned, everything you've gained, all that has changed... it's really something. In the working world, there really isn't any 'good time' to do this - every week, every month, flows one into the next, and you never get that feeling like "here's a stopping point, let me sit back and just think for a bit".
I'm sure some people will point to holidays, vacations, Yomim Tovim, and the like as opportunities, but they're really not - if you're working full-time, and especially if you have other responsibilities, you simply don't have the time to let your mind slow down like that. (Not to mention that you have no vacation days thanks to the Yomim Tovim.) You're rushing to make Yom Tov, then you're rushing to make up work from it, and you're traveling to see all the family you never really get to see, and you're catching up quickly with friends who you don't really have time to talk to... it's never ending. It makes you miss those school days with their 3-month summers and clear-cut semesters and goals and guidelines and assignments, if only to have that ending to just stop and reflect.
On that note, I particularly appreciated this beautiful post by my good friend Moshe about the lessons he's learned this past year, and on a similar note, these posts by Erachet, the Apple, and Chana. Check them all out.
UPDATE: And SJ, just after I posted this. :)