In a recent study of one million people around the world, researchers found that most viewed self-control as their biggest weakness and character failure.

"In the last 15 years we've discovered that [willpower] really is a form of energy in the brain. It's like a muscle that can be strengthened with use, but it also gets fatigued with use," says New York Times author John Tierney. "You only have a finite amount [of willpower] as you go through the day, so you should be careful to conserve it and try to save it for the emergencies."

Tierney and social psychologist Roy Baumeister recently co-authored a book titled "Willpower: The Greatest Human Strength," which looks at how willpower and decision-making are interconnected.

We pulled out some of the best takeaways, which Tierney covered in two excellent pieces for the Times ("Do You Suffer From Decision Fatigue?" and "Why You Need To Sleep On It").