" we all know that we should exercise, sleep eight hours, eat healthier, and be kind to others. But does this common knowledge make doing these things any easier? Of course not. Because in life, knowledge is only part of the battle. Without action, knowledge is often meaningless. As Aristotle put it, to be excellent we cannot simply think or feel excellent, we must act excellently. Yet the action required to follow through on what we know is often the hardest part. That’s why even though doctors know better than anyone the importance of exercise and diet, 44 percent of them are overweight. "

― Shawn Achor , The Happiness Advantage: The Seven Principles of Positive Psychology That Fuel Success and Performance at Work