"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."