I’ll intellectually/emotionally/physically hard as answers. For me its either 12 hours straight “punching tubes” on a very large scotch marine firetube boiler at the beginning of my career or Easter around a decade ago when I was working with troubled teens and had to engage in 5 separate protective holds in one 16 hour double shift. The former was all physical and the latter was a combination of emotional and physical.
I was chasing a bug. Complete showstopper for a new system in which we had invested a lot to be the next big thing. And the responsibility lay with me.
I wrecked my brain on the two weeks towards Christmas trying to get it stable. I tried every trick in the book. I tried some more things after Christmas. Nothing, absolutely nothing made the system any better. I started to get anxiety attacks and breakdowns. I cried at work. Four weeks of bug hunting, and still no idea what actually went wrong.
In the end, it turned out to be a crazy hardware issue, something I could not fix in any way with software. One part for a tenth of a cent changed on each board, and the system ran like a charm.
Boss gave me the rest of the week off to recover.
…in addition to the overtime cash, right?