People often underestimate risks too. I'm following a thread on another forum where a guy made his own solar power system. Seems like a risk that it might not work, but instead it burned his house down, oops. Fortunately no casualties.

You really have to play dungeons and dragons with yourself, thinking up imaginative possibilities of what might happen at every juncture. Don't worry about nuisance risks, but try to foresee the potentially catastrophic ones and mitigate them.