You probably know about the importance of diversifying when it comes to your finances. You understand, for example, that it's unwise to have all of your money invested in the stock of one company. But diversification is also important to keep in mind for your marriage. I was reminded of this truth while listening to a recent NPR Hidden Brain segment with Shankar Vedantam. He spoke with Eli Finkel, a social psychologist at Northwestern University, about how our rising expectations of marriage can create problems in our relationships.