Back when I was diving regularly, I used to follow the accident/injury/fatality reports pretty closely. Most "accidents" and/or fatalities were deemed a result of failure to follow procedures properly. Regardless of the cause, seldom was the victim able to provide a "reason" for his departure from training ("So tell us: Why did you hold your breath and shoot to the surface from 60ft of depth?"). The bottom line is, in most hazardous endeavors, we know more about why someone sticks to their training successfully (because they get to report) than about the things that cause deviation there from.
I remember a sky diver who accidentally left his parachute aboard the aircraft on his 500th jump; we'll never know why for sure (though the new video camera with which he was playing likely had an effect).
Now consider this. Most drivers have what for 'training'? Drivers ed? Are they taught say 4 hours of clock time on how to get out of skids? Are they drilled on how to keep brakes by using closed circut roads? Or any kind of real seriouis hands on training of that type? No right. They drive around town doing right turns and left turns and parking and... everything except practicing real emergencys. And we wonder why we have so many accidents on the roads.
Training matters, but as I pointed out, there are levels of training. And of course if you are trained to do the incorrect thing, or some real complacated thing, well you have better be very very well trained to pull it off.