In their personal-finance classic Your Money or Your Life (Penguin, 2008), Joe Dominguez and Vicki Robin argue that the relationship between spending and happiness is non-linear, meaning every dollar you spend brings you a little less happiness than the one before it. More spending does lead to more fulfillment — up to a point. But spending too much can actually have a negative impact on your quality of life. The authors suggest that personal fulfillment — that is, being content with your life — can be graphed on a curve that looks like this:
