My squib occurred after 30+years as a handloader; this happened only about 2-3 years ago. I had an unexpected chance to get to the range. I had wanted to do a ladder work-up with a .223/5.56 load but never got around to it. The range trip caught me unprepared so I quickly, too quickly as it turned out later, threw my test loads together. I used my single stage and loading block to load 50 rounds (I was working up the load for 2 different rifles) but, somehow, didn't powder one case. Got a "click", stopped, waited a moment for a hangfire, and ejected the round. Luckily the primer didn't push the bullet out of the case so I finished my work-up. When I got home I knocked the offending round apart and that's when I discovered I had never charged that case. No harm no foul. BTW, up until that day I had always followed the 4 rules you posted. 1-No distractions, I don't have a radio, TV or even my phone. 2-No alcohol/drugs 3-One bottle of powder at a time. The only rule I didn't follow was #4: don't rush. Thankfully I learned my lesson no worse for the wear.