Any person who is on a diet can tell you that strength is not just physical. Especially when a fresh batch of chocolate chip cookies comes out of the oven at her local coffee shop just as she approaches the register, or her office manager orders pepperoni pizza to celebrate a coworker’s birthday. But dieters may not realize that exercising their willpower will make them stronger.

Roy Baumeister and John Tierney explore the science of self-control in their new book Willpower. They note that people who exercise their willpower frequently often have better self-control. The next time you’re about to give in to an unhealthy temptation consider the great mental and emotional workout you’ll be giving yourself just by resisting…