No excuse, really everyone gets tired, sooner or later. With me, these days, it's sooner.
But my computer gets tired, too, I mean, the battery. And then it warns me: battery low or running on reserve power, and then it cuts out. People don't always cut out; they go on, doing shoddy work, yelling at their co-workers or children or dog, whoever gets in the way - or makes them feel guilty, more likely. There used to be an expression, "flogging a dead horse." Gone With the Wind comes to mind: Scarlett slashing at the horse to force it to go on. We don't have easy access to horses any more, at least, I don't, and dead batteries are not to be flogged. So we force ourselves, and wish for a clone. Do robots run on batteries?