Another thought prompted by my weekend College reunion
Of course, each of us uses anniversaries or regular reunions to get some sense of how we're doing - "oh, I can't believe I was with that girl, I'm much happier now" is a common internal narrative.
But what's really interesting is how readily and how thoroughly folk check themselves vs. other people:
Who still looks the same? Who's aged badly? Who's got a portrait in the attic? Who's still a c***?
Who's doing better or worse professionally compared to me? Or has a prettier wife/husband/labrador?
And even:
Compared to how we stood back then, is our relative position the same or better/worse than it was all those years ago...? etc etc
I make that at least 3 dimensions of comparison
And no, it's not just me thinking this stuff....Social proof is really important to our species - much more so than you or I would normally allow. It's how we tell all sorts of things about ourselves and the world and the relationship between the two. It's only human