Interesting. I quite like the feeling of nostalgia, giving an additional depth to certain situations. Though I remember watching the movie "The perks of being a wallflower", and having that painful nostalgia of my last years in high school. But generally, I cherish the memories I have a lot, and I enjoy re-living feelings from the past, especially the happy ones like you mention. And even in the not-so-fun ones, there's a comfort knowing that they're over.