The authors set up the entire premise of the book with a description of a scene from the movie “City Slickers.”

In one scene, Curly asks Mitch if he knows what the secret of life is.  Mitch answers no.  Curly then holds up one finger and says the secret to life is one thing, just one thing.

From this quote and through a process of discovery, the authors narrowed down their focus to this one question, “What’s the ONE Thing you can do this week such that by doing it everything else would be easier or unnecessary?”

The Domino Effect is the concept that domino falls can topple big things.  A domino can knock over a domino 50% larger.  In that scenario, the 57^th domino is almost the distance to the moon.  The moon is reachable if you prioritize everything and put all of your energy into accomplishing the most important thing.