Me too. It may take me all day to do 100 rounds, but I hand weigh and trickle feed onto a scale each and every load.Nobody is mistake-free, but when you handload as I do (grab a piece of empty brass with your left hand, dip and charge with your right hand and then set the brass in neat rows off to your left), it's hard to make a double charge. If the phone rings or you get otherwise interrupted, just finish the piece you are holding and attend to it. Of course, you still have to make sure you are using the right powder and dipper.
Glad you were not hurt.