Morgan Housel is on to something:

I have a theory about nostalgia: It happens because the best survival strategy in an uncertain world is to overworry. When you look back, you forget about all the things you worried about that never came true. So life appears better in the past because in hindsight there wasn’t as much to worry about as you were actually worrying about at the time.

Times were always simpler in “the good old days” because of how memory works.

When you see a nostalgia explosion, instead of jumping on the train, think about what it signals about how people are feeling.