Research has shown that kindness (along with emotional stability) is the most important predictor of satisfaction and stability in a marriage. Kindness makes each partner feel cared for, understood, and validated—feel loved. “My bounty is as boundless as the sea,” says Shakespeare’s Juliet. “My love as deep; the more I give to thee, / The more I have, for both are infinite.” That’s how kindness works too: there’s a great deal of evidence showing the more someone receives or witnesses kindness, the more they will be kind themselves, which leads to upward spirals of love and generosity in a relationship.
There are two ways to think about kindness. You can think about it as a fixed trait: either you have it or you don’t. Or you could think of kindness as a muscle. In some people, that muscle is naturally stronger than in others, but it can grow stronger in everyone with exercise. Masters tend to think about kindness as a muscle. They know that they have to exercise it to keep it in shape. They know, in other words, that a good relationship requires sustained hard work.
Emily Esfahani Smith writing in The Atlantic