I hate making mistakes. I especially despise mistakes when it comes to work.
I put in a request for quote for a customer and put down the wrong part number. Thus we quoted the wrong thing. Luckily, I caught the error before I sent it to the customer. But now I have to let various marketing types know I screwed up, and they have to duplicate work due to my mistake.
The only bright side of this mistake is the the discovery of my own error led to an impressive string of profanity on my part. It should have been recorded for posterity.