I see no wrong in reminiscing. It's a sign of acknowledging whatever that happened, be it good times or bad. Some people are just too self absorbed. They wrap themselves in their cocoon, telling themselves the world revolves only around them and that the past doesn't deserve any respect.(Of course unless it's about boasting about "that time when I achieved this and that") That's total bull. I say you're just plain selfish.
It doesn't seem to make any sense. How do you expect us to learn and rectify mistakes made, or to be grateful that you were once on cloud #9 and not take things for granted, if we didn't think about the past?
Our memory serves more purpose other than trying to cram facts and informations.
All the countless happy moments while in slackerdom didn't just happen for entertainment. The backstabbing, cat fights, arguments etc, have a story to tell.
Typical mentality would be to keep the good memories and ditch the bad ones. What for? That's just living in self denial. Just before you close your eyes for the last time, majority of us psycho ourselves into thinking that our live has been meaningful, sweet, fine and dandy. Why? Cos we choose to chuck all that nasty moments into one dark and dusty corner at the back of our heads. It'll be a sin to even think about it. It's better to live a life without any regrets, trails and tribulations. Stupid people with stupid thinking. Imbeciles.

*If it makes you happy, it can't be that bad