How do we design habits that pull us in rather than ones that fade away? Scientists have been studying this question for many years. While there is still much to learn, one of the most consistent findings is that the way to maintain motivation and achieve peak levels of desire is to work on tasks of “just manageable difficulty.” The human brain loves a challenge, but only if it is within an optimal zone of difficulty. If you love tennis and try to play a serious match against a four-year-old, you will quickly become bored. It’s too easy. You’ll win every point. In contrast, if you play a professional tennis player like Roger Federer or Serena Williams, you will quickly lose motivation because the match is too difficult. Now consider playing tennis against someone who is your equal. As the game progresses, you win a few points and you lose a few. You have a good chance of winning, but only if you really try. Your focus narrows, distractions fade away, and you find yourself fully invested in the task at hand. This is a challenge of just manageable difficulty and it is a prime example of the Goldilocks Rule. The Goldilocks Rule states that humans experience peak motivation when working on tasks that are right on the edge of their current abilities. Not too hard. Not too easy. Just right.