I think there are two main reactions when you realize you got old.
One is trying to make up for all the things you supposedly left behind, and the other is to really look forward to the future. New age brings fresh challenges.
To get old isn't just an age issue. To be old is to be mature enough to understand certain aspects of life you really weren't able to before.
I don't consider myself young, but I don't think I'm old either.
I still can't understand many whys and I'm still facing new challenges every single day. And all of that said, though, I'm already quite capable of comprehending many aspects of life I couldn't before.
And I'm independant enough to life my life and not someone else's.
So no. That would be my answer.
If I could do it all over again, I would.
And if I could get any younger, I wouldn't.