This happens when playing online Scrabble. You realize, a nanosecond after you hit the 'play' button, that you could have added one tile and gotten way more points.
During my turn I added an 'e' and and 'm' to the 'h' that was there to make the word 'hem.' I was scrannoyed the moment that I hit 'play' when I realized that I could have added a 'p' (which would have been put on a triple word space).
by barbg April 24, 2011