It’s nostalgia, a surprisingly powerful human emotion because it’s not as familiar as the everyday ones they talk about in kindergarten. When nostalgia hits, it’s later in life and you’re usually alone trying to understand it.
Yes, at 62 I find myself obsessing over my days at university collecting old texts on eBay and making playlists of old tunes. Nostalgia can take over your life but it does exercise your memory.