When I see an angry person, or a Taylor Swift fan, or a fifty year old, I tend to assume that they are thoroughly experienced and on top of enacting being that kind of person.
The fifty year old is an odd one out though: nobody has any previous experience being as old as they are now! Not only that, but all of their experience is of being younger. And granted, some of it is only a little younger, but a lot of it is a lot younger!
Everybody just stumbled into being this old. It’s their first day.
Does this cause ‘acting ones age’ to warp over time? Today’s 45 year olds have an idea what acting 45 looked like for the 45 year olds that came before them, but they are also very used to acting younger than that.
I'm "old" (60s), and I can tell you it definitely feels like my first day at it. Most people of my age that I talk to feel the same - our brains haven't caught up with the fact that we're supposed to be old yet. (My 90 year old aunt said she still felt 21, a couple of months before she died)
Expectations of how "old" people act have changed radically in our lifetimes - partly down to life expectancy, partly down to there being many more of us, so the spread is that much wider, partly due to wealth and health effects. When I was born, actuarial tables would have given my life expectancy as 66, but now I've (nearly) got there, I can reasonably expect to live another 20 years. So maybe it's appropriate that I feel 20 years younger than equivalently-aged people did in my youth?
I think the same is true of people in their 20s, too, by the way. Expectations of everything from age of marriage to housing to job situation have changed radically in the past 40 years. We're all still on our first day here.
I can't help but think of this https://youtu.be/TdIRrmNN_CQ