I think you are over thinking it. Sometimes, crap does happen. For my comfort with my mechanical ability, I'd say my confidence in myself is pretty high. But, you can't really prepare for everything. Instead, you need to prepare for what is most likely to go wrong and have a means of correcting the failure good enough to get you home or get you to a place where you can get help. For a 200k, I'd worry most about flats or a broken spoke. Neither of which is a big deal to fix or patch up.

Carry your cell phone and some cash.