Which isn't even half the age of the oldest person to ever live. I think quality of life at 60 varies a lot person to person. Of course your physical capabilities will have peaked, but that doesn't at all imply your ability to enjoy life has. Heck, I was reading a 100-year old recently completed a marathon, which is more than most my age (23) are capable of doing. I'm sure there are plenty of people who had a miserable youth but had very enjoyable years toward the end of their life.

>I was sick of having to dig through the trash to find an envelope that was sent to me so I could remember my own address - especially since I lived in the same place for the last nine years!

He felt done because he was using cliches about aging to rage at himself. There is no "prime" after which the value of your life declines. If your conception of yourself is that you only deserve to live insofar as you can perform as a young person would, you aren't admirably rational, you're just self-loathing.