Has anyone accidentally traded with themselves? I went to sell in a Eurex futures product and realized that it was my old bid that I had hit by mistake (and had forgotten to cancel). So I have a buy and a sell at the same price because of my sloppiness. I contacted my broker to report the mistake and wondered if the trade should be cancelled or if I would be punished. They spoke to Eurex and said there would be no fine and the trades stood, but that it should not happen again. Has anyone been hit by a fine or other punishment for something like this? Hopefully a one off on my part but there is always the small chance of it happening again (especially in the morning when I am half asleep). Is it something that I should be extra careful about preventing? Thank you in advance for any replies.