One book, The Happiness Advantage, explains what happens when your brain is faced with a daunting goal: The amygdala, the part of the brain that responds to fear, takes over the thinking part, the prefrontal cortex.
You can watch it happen on a brain scan. The more the amygdala lights up, the less the prefrontal cortex does.
Watch out how you set big goals or your people will freeze.
Source: Bob Sutton, Work Matters.