Pride before a fall

So there I was, finally getting it right and feeling pretty smug about it. All the pages had nice little ticks and a red remark at the bottom, confirming all the details were present and correct. The very serious computer system did its fancy thing (after a painful pause for thought) and then I discovered I had made a mistake. A great big howler of a mistake caused by not checking what I was doing carefully enough. And now I don't know how to rectify it without professional help.

That little smug smile I had earlier in the evening? He shot out the door faster than the blink of an eye. Curses.