One key discovery is that self-control is an exhaustible but buildable resource. A psychologist demonstrated this with a clever experiment. He had college students skip a meal, so that they felt hungry, and then sit at a table. The table had freshly baked chocolate chip cookies, candy, and radishes.

The first group of students—the lucky ones—could eat whatever they wanted. Of course, they only ate the sweets. The second group had the same food in front of them, but they were told to leave the sweets alone, and they could only eat the radishes. The third group had no food in front of them at all. (It was the control group.)

After the students sat at their tables for a while, they were given a complex geometry problem to solve. The trick was that the problem was unsolvable; what mattered was how long they worked on it before giving up. The students in Groups 1 and 3 worked for about 20 minutes. But, the students in Group 2 worked only about 8 minutes. Why such a big difference? The students in Group 2 had already used up a lot of self-control resisting the sweets, so they had less energy left over for working on the geometry problem. Researchers call this ego depletion.

Does this mean that self-control, once it’s used, is gone forever? Not at all. It recharges with rest. In fact, the more often self-control is used, the stronger it gets. Self-control is like a muscle. It weakens immediately after use but strengthens with frequent use.

Possible Preaching Angle:

The strategy is simply being aware of our capacity for self-control and willpower throughout the day. Keep an eye on the gas gauge. Knowing our willpower level tells us when it might be a good time to take on new challenges, or when we should stop and refill. It lets us know when we are most vulnerable to moral failure.