All sorts of things come to mind, about all I can do now is write checks and repeat old stories that even bore me.
I guess the thing I miss most is the ability to pull an all nighter when I need to get things done. That used to be pretty standard procedure when the apartment needed painting or I needed a zillion Christmas cookies. I would come home from work and start a project that would last all night and half of the next day with energy to spare.
I used to get into bed at night and be sound asleep in less than 15 seconds. My next conscious thought was 7, 8 or 9 hours later to shut off the damn alarm. Now I'm lucky to sleep for a two or three hour stretch without waking up.
That's the "G" rated version.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan
Andy, I was just going to post the same thing. I used to go to bed and fall asleep within minutes, and sleep thru the night. (and not very long ago) Now, it takes me a while to fall asleep and even if I limit fluids in the evenings, I'm still up every couple of hours to...well, ya know...
Running, too...I wouldn't even attempt that anymore. sigh....
Grandchildren fill the space in your heart you never knew was empty.