A great song done by Pete Seeger on the Pete Seeger and Arlo Guthrie Live at Carnegie Hall album:

How do I know my youth is all spent?
My get-up-and-go has got up and went,
But in spite of it all I'm able to grin
And think of the places my get-up has been.

I wake up each morning and dust off my wits,
Pick up the paper, and read the obits.
If I'm not there, I know I'm not dead,
So I eat a good breakfast and go back to bed.

...there's lots more, but that's all I remember.

Robert Lee