According to the lyrics of a popular song "when a man loves a woman there ain't nothing he won't do, he'll turn his back on his best friend if he puts her down" (When A Man Loves a Woman, Percy Sledge, 1966 "If Loving You Is Wrong"). This song illustrates the honeymoon period in the beginning of a love relationship between a man and a woman. The lovers start out obsessed with each other and the new relationship. As the relationship continues over time, one or the other begins to experience diminishing returns on time spent together and long for separate time on other activities. This is often the point where the couple decides to get married thus cementing the relationship while reducing the exclusive time commitment, or the couple breaks off the relationship and begins the search for the perfect love again.

I believe that this transition in the man-woman relationship is a good way of illustrating the law of diminishing returns. The law of diminishing returns states that holding one factor of production constant, as additional units of another factor are added, output will increase but at a diminishing rate. To apply this to a relationship we might say: As equal amounts of the variable input (time with lover) are added and the relationship remains stable, the resulting increments to output (satisfaction with how time is spent) will diminish.

Many people think that this drop in level of satisfaction is a negative in a relationship and that something is wrong with the relationship if the couple does not want to spend all of their time together. I believe the law of diminishing returns actually ensures a more stable society. If everyone fell in love and was obsessed with the loved one for decades, very little work would get done. A person would become obsessed with a loved one, particular job or idea early in life and never have time for anything else. The fact that we receive less and less satisfaction from something as we spend equal amounts of time on it ensures the onset of boredom and fosters creativity.