For example, suppose you increase your flying from 50 hours/year to 500 hours/year. Even if you thereby reduce your hourly fatality risk by as much as 80%, you've still doubled your yearly fatality risk.
I discussed the subject of "undesirable occurences" with one of the older CFIs, 30+k hours, 40+ years doing it. He has three accidents on his record - one was a flat out broken landing gear on a 172RG where one of the mains wouldn't come out - damage from the landing was sufficient to classify it as an accident.
Second - came in to land at a grass strip, people on the ground were pulling a glider out to launch, figured he'd land past it, then figured there's not enough room and went around, hit the fence at the end of the runway with the mains doing so, ok landing afterwards but enough gear damage to be considered an accident.
Third one - friend's student asked for a "second opinion" day before his Commercial checkride, this CFI flew with the student before and knew that the performance was good and wasn't expecting any surprises. In a power-off 180 the student abruptly pulled the yoke and stalled the Arrow about 10 feet above the runway, hard "arrival" caused the gear struts to go through the wings.
#1 was a one off "happens" deal, #2 and #3 were back to back pretty much. His opinion on the subject - complacency.
My point is, at some point of having more flight hours a year, you get complacent and screw up. Not saying "don't fly as much as you can" but rather "remember that you are getting complacent and fight it"