A recent one and an old one.
1. I was making chocolate mousse for the first time last weekend. Even though I was repeating the recipe instructions, mantra-like, to avoid divvery, I still found myself putting the separated yolks into the mixing bowl while chanting "whisk three egg whites with a pinch of salt, whisk three egg whites with a pinch of salt..."
2. While building up a bike yesterday I definitely didn't cut the long (rear) mech cable to use on the front mech, thus leaving myself with a front mech cable for the rear mech. I'm not being sarcastic - I really didn't do that. But it's only because I've done it so often in the past (well, maybe twice) that I will never do it again.
Probably.