Ah yes... the mistakes you only make once. I have several of those. The good thing is if you survive the Once, you're home free. My most recent was attempting to put a solar filter on the eyepiece of a telescope instead of over the lens and pointing it at the sun. It burned a hole in the filter in half a second. Luckily it was the half second BEFORE I put my eye to the eyepiece and not after....take a piece of wood you need to put a hole in, sit in on your lap, then drill through it into your leg.
Had to look up the cultural implications of what I've just learned is "riding the short bus" to figure out what you were implying. Was pretty confident it wasn't going to be anything good.