I think for people who don't stagnate and continue to progress throughout their lives, nostalgia will be limited. People who peaked in High School (for example) and stagnated in life afterwards will probably tend to look back on their past years with fondness.

I see this with people in the town that I grew up in who couldn't get out. After High School, they largely languished in the same town and haven't really done much with their lives since. I see them talking about past years and High School with far more regularity than the more successful people I know. The successful people on the other hand - they bring up the future more than they bring up the past. That's probably because they have something to look forward to on the trajectory they're on - it's a mental state, a mindset.

Now this is a very simplistic version of my observations but it's what I've seen so far. I'd love for people to bring in some kind of science to this theme that I've observed. My observations could certainly be isolated and wrong but from conversations I've had with other friends from similar smaller towns, they've reported observing similar things.

Your observations strike me as all too accurate due to my own anecdotal experience. I've tasted both sides of the coin. After leaving a phase of torpor that lasted years and started taking life into my own hands, my mindset completely changed to the point where my past self feels almost alien. The effect nostalgia had on my daily life essentially went from a driving force to a non-factor.

I would still add the disclaimer that you may simply not be old enough- after recent experiences with my elderly & currently very sick father.

When you get older your body wears out, even if you take care of it. You may not notice it as an active 40 year old but you definitely will as a 70 year old.

Other things like culture and values change around you and you can't always keep up, causing the feeling that "the world is going to hell". Maybe your field was doing great 20-30 years ago and is now on a downward trajectory (again you can't always plan for that decades in advance).

It doesn't have to be that way but getting old at some point does suck for most people, some earlier than others.

You're right, of course. The idea of slowly degenerating and becoming irrelevant like this has filled me with a sense of dread for a long time, although I've largely accepted the inevitable now.

I would say I'm attempting to get at least one decade of vaguely defined "intense" living. If I can get that it would already be more than what a lot of people get!