I'd say that it's very natural to want to retire after 40 years of doing anything. You reach your various ceilings. You have most of your enthusiasm spent, most

I'd say that it's very natural to want to retire after 40 years of doing anything. You reach your various ceilings. You have most of your enthusiasm spent, most tasty bits of your area of expertise picked and consumed, seen many sad things repeating over and over, etc, etc. And any major new development may be disheartening, whatever it may be. I think this is fine. A person, having worked for so long and successfully on something, has every right to call it quits and switch to something else. Something fresh and different. Godspeed!