" This concept upends the way most people think about their subjective experience
of life. We tend to place a lot of emphasis on our circumstances, assuming that what
happens to us (or fails to happen) determines how we feel. From this perspective, the
small-scale details of how you spend your day aren’t that important, because what
matters are the large-scale outcomes, such as whether or not you get a promotion or
move to that nicer apartment. According to Gallagher, decades of research contradict
this understanding. Our brains instead construct our worldview based on what we pay
attention to. If you focus on a cancer diagnosis, you and your life become unhappy and
dark, but if you focus instead on an evening martini, you and your life become more
pleasant—even though the circumstances in both scenarios are the same. As Gallagher
summarizes: “Who you are, what you think, feel, and do, what you love—is the sum of
what you focus on. "

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