This quote stuck with me. Time is scarce, and I certainly didn't want to kill any.

At West Point, one way they'd punish deviant cadets is to have them march around for 3 hours and not accomplish anything. It isn't that the march is physically or mentally tiring/uncomfortable, it's just that they're so busy and have so much to do that 3 hours of unproductive marching is felt as punishment.

See 32:30 of this podcast.