I tend to smurf up with drying clothes that shouldn't be tumble dried. They're washed on a lovely 40 degrees setting but then get exposed to drying temperatures meant for cottons at times in excess of 120 mins. Whoops.

Most other mistakes I'm pretty good at avoiding, tbh, if I wasn't? I'd have lost my job by now (99.9% + quality target 100% of the time). The other Steve classic though would be keys. You know it's gotten bad when the landlord installs a spare key outside the front door in a number lock safe that you have the code to so you can get in if you do it again.