Accidents happen, that's why they are called accidents. Otherwise we'd call them deliberates.
Accidental discharges are just like any other accident. There will always be accidents as long as humans are involved.
Despite their truth, I don't like these statements, gym and onebigelf (John), with all respect. They can be read as having a "s--t happens, what can you do?" attitude, not the best attitude to prevent ADs. And attitude is crucial.
Car accidents are probably close to what most people think of by "accident." Whether or not you have a car accident can be heavily determined by road conditions, weather conditions, and the actions of others--all of which are beyond our control. (Still, in MOST of these situations the driver might have significantly reduced his risk of accident by changing his behavior: driving slower, pulling over if visibility was poor, etc.)
ADs are generally NOT like these other accidents: except for that rare unanticipatable mechanical failure in a well maintained gun, ADs are preventable, and they are our fault. Most involve the shooter pulling the trigger when the gun was thought to be unloaded. Others may involve placing your finger on the trigger without intention to shoot, and then you get bumped, startled, whatever. And almost ALL injuries from ADs can be prevented by keeping the muzzle pointed safely.
We should, all of us, put as many reasonable behavioral obstacles between us and ADs as we can, so that more than one safety behavior has to break down to allow an AD. Even if that means rechecking the unloaded status of a firearm a seemingly unnecessary number of times (like I do), and going through ridiculous contortions to prevent muzzle-crossing any part of a person, even in gun stores.
Safe training and FREQUENT safe practice are keys. And an "I can prevent ADs" attitude beats the heck out of "Accidents happen" (even though they do).
Be safe.
"A seemingly obsessive concern for safety is the mark of a professional."--Massad Ayoob