" You have a finite amount of willpower that becomes depleted as you use it. Your will, in other words, is not a manifestation of your character that you can deploy without limit; it’s instead like a muscle that tires. This is why the subjects in the Hofmann and Baumeister study had such a hard time fighting desires—over time these distractions drained their finite pool of willpower until they could no longer resist. The same will happen to you, regardless of your intentions—unless, that is, you’re smart about your habits. "

― Cal Newport , Deep Work: Rules for Focused Success in a Distracted World