Tangentially, the physical labor jobs I had when younger never really tired me out the way that the mental/bureaucratic/political job I have now does. Physical work actually energized me, I mean this is all confirmed today as well, we know all the benefits exercise brings on well being. There's something about desk jobs that is frankly soul sucking and literally mentally draining in a way where when the day ends, it'…
this may be the key. When I was younger, I don't remember getting tired much no matter what I was doing, programming, studying, gardening.