Me looking at my cool gray hair in the mirror and realizing I have outlived the highest possible age I at one time believed I would ever achieve by well over a decade: Omg I love being old

Me attempting to use my knees for any purpose: Omg I hate being old

@mcc for the latter: exercise helps!
@PeterSommerlad as long as it's not jogging on concrete, yes…
@mcc @PeterSommerlad the fraction of my time that I have to spend doing squats in order for my knees to allow me to do any other exercise seems to go up dramatically with age. By 50 I expect to spend just as much time on squats as on whatever activity I actually want to be doing.