The worst thing that has ever happened to me on the firing line is a .44 mag that didn't get a powder charge. Pushed the primer out of the pocket and jammed up the cylinder a bit. No harm to shooter or firearm.
One thing that keeps me safe is that i absolutely do not choose powder charges that will allow me to double charge a case. If i double charge a case, the powder will be all over the reloading block and my bench.
This allows me a little bit of flexibility with distractions - which are sorta common in my house with 2 cats, 2 dogs, and a wife.
One reason I like TiteGroup for reloading 9mm. The charge I use fills slighly more then half the case. If I where to double charge it would be obvious. That's why I check every case before I seat a bullet.