I'm heading towards 40 and frankly if my 40's are anything like my 30's have been I'm looking forward to them. I wouldn't go back to being in my 20's for anything.
I don't care what age I am, I'm grateful to make it this far and I look forward to getting older. If I'm no longer attractive to people in their early 20's that's not for me to decide.
I read a tweet the other day from someone who said something along the lines of "I'm sure people go home and masturbate to your personality". It was in reference to someone who had said they were happy to be 38 or something. I thought to myself then, "fuck it's so much work being a young kid, knowing everything, being cynical, being worried if people are masturbating to you or not."
I like that as I've aged I've grown my comfortable in my own skin. For the most part aging hasn't been the end of my life. It has been the end of certain things, but the opportunities I've come across mean a lot more to me than the transience of my "pretty" days did. That said, I was just as obsessed with youth and beauty when I was young.
The trick I think is to realise the changes to your life that occur as you age aren't the end of anything, but the beginning of a whole new adventure. So long as you are comfortable with how you've turned out, nothing else really matters.