About 2 years ago on a commute, I had just turned in to the Greenway. There is an sharp S-curve there as the path drops about 15' and a jogger ahead at the end of the curves. Since it drops you can see everything around the curves to the end, and I always check at the start of them. It had rained earlier so I was being very cautious and had already seen the jogger so I was approaching at around 8 mph, maybe less. Swinging wide to pass, I thought I was crossing the painted line completely vertical, and straight on. Nevertheless, my front wheel shot out from under, catching me so off-guard that I didn't react at all and landed square on my side. On the outside of my shoulder, breaking the collarbone (which had been broken a couple of years before, in the same place).

The lesson, even if you are alert and fully aware of the dangers, and doing everything "right", you still need to be ready. And I pass between the lines now if I can, in any conditions, and not at all on curves, even those with good sight-lines.

The other lesson I took from it was more specific to me, a realization that I needed to strengthen my skeleton since it really shouldn't have broken from that impact.

My first ever mishap, was when I was a newbie learning the hard way, and the lesson that we all know but a huge surprise at the time. I was just chugging along with a serious load of groceries, right-hooked went over his fender and rolled across the road, and the guy didn't know he'd done anything wrong until the cop explained it. I'd been driving since the 70's and yet I never expected that someone with a license, who was not impaired or horsing around, could pull a stunt that stupid let alone think it was blameless. But as we know, many drivers are routinely idiots around bicycles.