I had started my business and things were going more slowly than I'd imagined they would. So slowly I needed to take a job to pay for rent and food and the salaries of some very part-time staff who were essential for various reasons. So I picked up a teaching gig at a small private training school that brought in foreign kids working on ESL and dumped them in small group classes while they got ready to attend real schools.
The money was not great, but I rationalized myself into taking the work because the teaching time was compressed so I could work from 9-4 each day and then cram away at development until 2am or so. Or that was the idea. In reality the job was a massive psychological drain. There were no textbooks or support of any kind so doing anything half-decent required a lot of energy and creativity. Meanwhile, doing a bad job would have meant letting down the kids and being actively complicit in a system that functioned primarily to separate their parents from their parents' money.
It wasn't what I had signed on for, but it seemed easier to push through and try to do the best job I could than back out. The work was only a month or two, and what other choice did I have, I asked? And so it happened that as I walked in to class one day about three weeks after starting I literally burned out in the hallway. I had just dragged myself out of the stairwell when I suddenly felt like the bottom of the world. I was tired and depressed and exhausted and all of a sudden found myself perceiving myself from the outside and looking down and pitying myself at the same time. Before that I'd been able to shelter myself from those emotions by convincing myself that my actions were positive sacrifices that were necessary to start the business. But in that moment I saw my defenses as pointless delusions. I felt like a dead man walking. I was clearly the world's biggest failure. Career. Business. Whatever. Anyone with any sort of objectivity would have to agree.
I stopped working there after that first class wrapped up, but the money paid the bills and helped get me to the break-even point, or what I managed to convince myself was the break-even point. I don't think it is as bad as coping with bankruptcy or death or anything, but it was my lowest point and I don't want to go any lower.