This might not be a normal burnout story, so sorry ahead of time. I'm not mentioning any names of individuals or companies, so please don't ask. They are all

This might not be a normal burnout story, so sorry ahead of time. I'm not mentioning any names of individuals or companies, so please don't ask. They are all well-known, though. I partnered with a proven businessman for a project that took more than 5 years and about 8 hours per day, every day (I was already working 8 hours per day at my daily job). The deal was 50/50. We had great early reviews from media but only a handful of sales, like 5. He kept adding features because he said that's why we didn't have sales. The new features did not bring us sales. In the end it was my fault. He was known for being ruthless and litigious. When his attorneys came calling for full source code I caved and gave it all away and walked away from the partnership. It ruined a friendship or two, was tough on my marriage, and for a time I was suicidal. He never made any money on the product itself and ended up losing the code. I did not keep a copy. He sold a few of the patents here and there and they're in use by companies that if I mentioned the names your eyes would get big. They have incorporated some of the technology into products, but not all of it. I have no idea what he made on those deals. It absolutely killed my creativity. That's been 15 years ago and I still can't get motivated on any side project at all. I still am not completely whole.