I'm in a similar place to the OP. I turn 50 in a week. I get told often I look in my 30s. The majority of my friends are in their 30s. Hung out for 6 months with 28yr olds forming a startup last year, they asked me to join them. With few exceptions I don't fit with people my age.

What I find frustrating is the society at large won't let me ignore my age. You get categorized all the time. Some meetup or dating event is 30-45. Some form has age categories. Visas to visit countries have age limits (as in we let students in but you're clearly too old to be a student). Articles all the time tell you who you should be, behave, for your age. Others tell you if you're XX age you can't do that anymore. Whatever it is. Can't go back to school. Can't learn a new language. Can't join a start up. Bla bla bla.

Sure, most people's first reaction is "ignore that" but it's oppressive. It's a viral meme that eats at your thoughts

Big life decisions are also harder because you start to realize each choice cuts off others so which choice to make?