You are the sum of your habits. When you allow bad habits to take over, they dramatically impede your path to success. The challenge is bad habits are insidious, creeping up on you slowly until you don’t even notice the damage they’re causing. Breaking bad habits requires self-control—and lots of it. Research indicates that it’s worth the effort, as self-control has huge implications for success. University of Pennsylvania psychologists Angela Duckworth and Martin Seligman conducted a study where they measured college students’ IQ scores and levels of self-control upon entering university. Four years later, they looked at the students’ grade point averages (GPA) and found that self-control was twice as important as IQ in earning a high GPA. The self-control required to develop good habits (and stop bad ones) also serves as the foundation for a strong work ethic and high productivity. Self-control is like a muscle—to build it up you need to exercise it. Practice flexing your self-...