Technically, those aren't mistakes, they're slips and lapses. You know what to do, but you end up not doing it (like me leaving off the inner part of the airlock several batches ago). To me it's interesting how many of these stories involve leaving out the yeast--a critical component of fermentation, but one that appears several hours into a very involved task.
I too do not BUI (and I brew alone) and yet I have still caught myself about to pour hot water in a mash tun with a ball valve set to full open, etc. I wonder if it's a case of a complex task performed just frequently enough to establish a routine but not quite frequently enough to gain the muscle-memory to perform it automatically when our mind drifts elsewhere for a moment.
Anyhoo, I recommend checklists -- in your case, with pictures and equipment manifests