I haven't been riding long (new this year), but this question does run through my mind pretty much every time set out. To me, it's a good thing, as it keeps me more alert to what could happen, vs thinking 'it will never happen to me', and then missing something that happens on the road.
missunfinz also makes a good point (post above), in that a lot of accidents that are reported are due (in some way) to the rider themself, and there might have been something they could have done to either prevent the accident or reduce the risk/aftermath:
- Wearing proper/full gear vs nothing at all/minimal gear.
- Riding with the limits vs beyond their skill set or weather conditions.
- Refraining from drinking and riding.
- Refraining from speeding, lanesplitting, aggressive riding.
- Giving a car the right of way even when they are in the wrong.
- Treating all cars/vehicles as unpredictable, and expecting other motorists to play by the rules of the road/know how to actually drive a vehicle.
- Riding with proper training vs without any or even a license (I think HURT included this one, shocking as it is).
- Not buying a motorcycle that is well beyond your skill level (in my RTI course, they mentioned how one guy a few years back could barely ride a CBR125R but had already bought a Hayabusa).
Note that I am not saying the rider is always at fault (quite typically they're not), however there are things you can do to reduce the risk. Another good example is trying to make yourself more visible at intersections, since there is always the risk other drives didn't see you.
Really, all you can do is take control of what you can control, ride as safely as you possibly can (knowing you are the smallest thing out there with the least protection), and whatever will happen will happen.