The first time I picked the wrong co-founders (friends and all were engineers).
The second time I picked the wrong project.
The third time my co-founder died.
The fourth time I wanted to do it alone but I almost burned out before my family started to send the signal that it was time for a change but I still think the tech and project are excellent though.
He had a scooter accident. My feeling is that he probably had the accident because he was really pushing himself too much: he was barely sleeping 3h per night and in the end his life was totally unbalanced with lots of prescription pills to support it (sleeping pills, caffeine for day time, weight loss pills, etc).