I finished a painting on Friday after a week spent up in the mountains (without internet distractions) specially to finish the piece: frog monster slayer for the Game Challenge 2016.
I was so happy to post him finally as my final submission when i realized that the deadline was not the 25th, but the 21st... Not a few hours... DAYS away! Not even worth contacting the organizers claiming internet fail. 
How does it make me feel? Just plain stupid... for not having double checked the date, for not having put a reminder in my calendar... And for having put so many hours into a challenge project only to miss the final submission.

On the bright side, i did actually keep the deadline, even if it was the wrong one. I did do a good job with this piece and learned a lot from the work i put in. It was "only" a personal project, so no impact on a customer, and no money lost.
And I definitely learned a lesson: always double check and write down deadlines for projects!

Any one else care to share their Deadline Fail?