Imagine every morning, you have an "energy bar" floating above your head. This is not unlike a video game like The Sims or whatever where it represents a character's energy levels. But in this case, this "energy bar" represents your decision making abilities. Every decision you make, whether large or small, takes up a little tiny bit of energy. "What am I going to wear? What will I eat for breakfast? Lunch? Dinner? What am I going to say to my client at my meeting this afternoon?"