Share your dumb maintenance errors!

Changing the rear diff fluid, I remembered the amount to fill incorrectly and was a quart short. Wife was out of town and I had to be at work within 2 hours (it's a job where the previous shift couldn't leave until I got there). Shamefully borrowed a neighbor's car to go to the store for the last quart. I bought 2, lol.
Though it was my previous motorcycle, still kinda related

I tried to loosen the oil filter for about an hour, tried several different ways including stabbing it with screwdriver, didn't work.

An hour later, realized that I was tightening it, but I stabbed it from so many different angles now it was really hard to loosen it as there was no place to hold or stab, it was about to split into half. Luckily I was able to remove it after several attempts.

Now I only use oil filter tool to remove the filters, no more oil filter removal anxiety when I change the oil, it works like a champ for both cars and motorcycles.