Over at Simple Justice, Scott Greenfield has a terrific post about growing older and staying fresh, ambitious, and engaged. Here's a taste:

  For you generation Y's, or Q's or whatever they call twenty-somethings today, I have a surprise for you. In your mind, you never really get older than about 30. Sure, your eyes don't work as well, and parts of your body hurt in the morning that you never before realized you had, and you can't remember your kids names. But your brain tells you that you're still alive and vital. You try to lift things that will throw your back out for weeks because your brain says you still can.
  There are rights of passage that propel us to move forward. Remember that first kiss? It was electric. You want to feel that charge run through your body again. No, not by cheating on your wife, but by doing something you've never done before. There are a million challenges out there that I have yet to meet and overcome. I want to feel the energy as I stare them down, and the exhilaration as I prove that I can still do anything I set my mind to.
  My mind will always have the accumulated knowledge and experience gained over 50 years, and I can now see how this can be applied to so many new and different things that would not have interested me 25 years ago. So many things are far more fascinating to me today then they were years ago, when my focus was too narrow and my interested muddled. Back then, education was something to put up with as I pushed forward to whatever I would ultimately be. Today, it is like food to a starving man. Why didn't I learn so much more when it was all there for me to partake?
  I'm ready to do it all again, just like everyone else my age. Not a do-over, as I don't want to be 21 again, foolish and ignorant, too full of my self-potential to appreciate the joys of youth and how little I understood about the world. No, I want to do it again knowing everything I know now.