I'm 43, so not quite as old as you yet, however, I don't feel any different to how I did when I was 21 and I don't expect to feel any different when I am 60. I am who I am right now and that's it.

I think your issue is your expectation of how a 53 year old should feel is different from the reality. Seems to me you're exactly where you should be on your life right now.