Sign of getting old

My whole body is aching now. Spent the whole day with a premature 1.5kg day 5 baby with ileal atresia. Yeah, we have a new paeds surgeon from India. Very nice person. It is good in one sense, I can brush up my rusty clinical skill. But it also meant that we have more work. And I am getting easily tired these days-a sign of getting old! or a sign of complacency