via The Pmarca Guide to Personal Productivity:

What you do is this: every time you do something — anything — useful during the day, write it down in your Anti-Todo List on the card.

Each time you do something, you get to write it down and you get that little rush of endorphins that the mouse gets every time he presses the button in his cage and gets a food pellet.

And then at the end of the day, … take a look at today’s card and its Anti-Todo list and marvel at all the things you actually got done that day.

Thanks for the tip. I believe in the power of the done list.