Sometimes your best photos are those that you didn't completely prepare for. Your mind may have been preoccupied with other events or tasks, and so it may have been a blank slate regarding the event you were shooting.
I tore through a few cards at a friend's son's pee-wee game, and was actually pretty happy with some of the results. It's amazing what will happen when you don't pressure yourself.
Tell me about one of your favorite shots, and post a link. Let's see what you've got!