At one point does the things we do start to become nostalgic? For me I'd say I felt it at age 20 in very small hints, then more at 22, then a shit ton at age 26. They all pretty much consisted with major events... the first major events of my 20's. Where I was literally being reborn.
From a spiritual and psychological one, I would say for me at least, craving nostalgia brings me great comfort when I'm going through the most uncomfortable and rebirthing into a new person moments.
Hell I crave nostalgia I never even lived through or was too young too remember, or was aware but couldn't participate (hello Myspace!) Okay actually Myspace isn't a good example because its not like I couldn't have gotten onto Myspace, it's just my childhood was strict.
But you hopefully get the point.
The most recent one for me, I went through a nasty breakup and it made me look at my core self, and what do you know I'm craving the decade I was born in but have no memories of. And honestly all the parts of me, my childhood, my teen years, my early twenties. I'm craving it all, wringing all the nostalgia out of the goodness of my memories in them.
Therefor I think what I need to do is indulge the 90's nostalgia.
Then with 22, I was going to ages 5-10 version of me with nostalgia searching. Really decorating my room pink how childhood me would have dreamed of. Y2K clothing. Experiencing some of the most vivid joy of my life.
Then 20, looking back and realizing my teen years were really gone. Realizing my teen years were nostalgic. Thinking of my Tumblr I had, pre-chronic illness me body feelings, the mustache accessory phase I had (I had suspenders and a ring lmao).
So I think nostalgia can be a spiritual experience, it's dealing with the good parts of memories and reliving through them by thinking of the item of nostalgia (buying it, playing with it, listening, watching, etc).
Talking to others about nostalgic shared experiences can be a healing process as well. There's no wonder there's such a focus on generations (Zillenial here, Millenial/Gen Z, yes I don't fit in either 100%).
However I do wave a hand of caution towards going into your nostalgia. Know that it's become capitalized with the rise of TikTok. Capitalism has gotten its grimy fingers on it and waved things above our heads shouting nostalgia from the rooftops. So be careful about your purchase and attention consumption.
It's also good to make sure you stay grounded in reality, remember we cannot go back in time. Move in the present with gratitude and excitement, but also cherishing the current moment. Our time now will be nostalgic to us later on (or at least I'm hoping it will be!).