Have you ever wondered if there are lessons to be drawn from behavioral economics and the managing of interpersonal relationships? Relationships often fall apart for a variety of reasons, ranging from poor communication and mismatched values to external pressures and personal growth. However, one of the most fundamental yet overlooked reasons relationships deteriorate is the economic principle of diminishing marginal utility (DMU). This idea, taken from microeconomics, suggests that as an individual consumes more of a product or repeatedly experiences something, the additional satisfaction gained from each extra unit diminishes. Applied to relationships, this principle implies that the initial emotional excitement, appreciation, and fulfillment partners feel generally decrease over time, frequently resulting in dissatisfaction and, eventually, separation.