Tricky.
It would be difficult, because as I know, having had more life than I am going to get going forward, it is all my experience of life so far that makes me who I am.
If I were to stop at say, twenty-three when I was really happy and enjoying a wonderful single life, I would never know the utter joy of marriage and children, or the utter heartbreak of losing people I cared about - both of which go to making me who I am now.
So hypothetically, obviously, I am going for twenty-three, and when life either stops there, or moves on and all my friends and family go old without me moving with them, I won't have to worry, because this is just an interesting question - reality makes it far too complicated!