I'm currently going through the junior year of my high school, that was 20 years ago exactly. It has been 22 years since my favorite baseball team, the Boston Red Sox, had finally broken their Curse of the Bambino in 2004. The Harry Potter main book series ended 19 years ago while the film series ended 15 years ago.
When people stopped seeing me. If they notice me at all, they immediately avert their gaze and look right past me. I used to get more attention than that.
Whenever someone posts "Are you this old?", and it's a picture of an original iPod, or an original Razr, or similar.
When I remember my son is the same age I was when I got married.
When I think about how many pets I've had, and they're all dead now.