You struggle to change a rule once established.

Mental set, or the Einstellung effect, happens when you become fixated on a single approach and fail to see simpler, alternative solutions.

In experiments, participants repeatedly solved math problems using a complex method, even after they were introduced to a much faster, direct route. You become so accustomed to the mechanics of your initial successful effort that you essentially blind yourself to better options. Your brain prioritizes the familiar over the efficient.