According to the decision quality paradigm, applying your initial motivation to the process of achieving your goal is more effective than just doing it. The well-known Nike slogan is great when you're gearing up for a daily workout, but it doesn’t lead to sustained motivation needed for real fitness and weight loss changes.
Everyone knows they need to eat less and exercise more, yet doing so is much harder than it sounds. The Gut Check! rule is a way to stop allowing excuses to run your life. Try it for one day.