I think everyone suffers from this, and it gets worse as we get older. Nostalgia is the great silent killer. I forget where I read it, but I recall an article that surveyed successful entrepreneurs and business people and found that they had low, or nonexistent, levels of nostalgia when compared to their peers.
No matter how good life is, there is a great level of despair that goes unacknowledged in losing your youth because it is the one thing you can never get back.
However, its more than just getting old. It is the loss of hope. As teenagers, we knew that, no matter how much things sucked, they were virtually guaranteed to get better when we became adults. Unfortunately, we got there, and figured out that wasn't the case. Nostalgia is all about the restoration of hope - since we cannot restore youth, we try to restore the hopeful mindset that allowed us to achieve more at that age.