Four and What?

Sitting, listening to Crosby, Stills, Nash and Young
I’m transported back to the days of my youth,
when times were mostly confused, future cloudy.
Clear in the sense that I was alive,
looking forward, not behind…
when I heard the song I wasn’t alive four and twenty years ago,
though now I am – much more – three score and ten.
Still, I can’t go back. Even if I could, I wouldn’t.
No, going back would surely be a waste
hardly worthwhile.
For what I would have liked to change
is now gone, passed away…
The best I can do? Not make the same mistake…
no, not in these… final years.
What? Final ten of my life, if even that?