Therefore, leaving will be bittersweet. I don’t think “He retired after 52 years” needs an explanation! But in short, here it goes anyway: For many of us, old age eats up both physical and mental energy. If that energy is what you’ve always had in greatest amount, and your standards don’t change with the calendar, the result is that the work – getting done right – keeps getting more and everything else gets less and less. Nobody’s fault.