People sometimes ask me, “So you mean it doesn’t matter how I treat my child?” They never ask, “So you mean it doesn’t matter how I treat my husband?” or “So you mean it doesn’t matter how I treat my wife?” And yet the situation is similar. I don’t expect that the way I act toward my husband today is going to determine what kind of person he will be tomorrow. I do expect, however, that it will affect how happy he is to live with me and whether we will remain good friends.

You can learn things from the person you’re married to. Marriage can change your opinions and influence your choice of a career or a religion. But it doesn’t change your personality, except in temporary, context-dependent ways. A man might be tender with his wife and tough with his employees, or vice versa. A woman married to a man who constantly belittled her might look sad or worried whenever she was near him. If she stuck with him despite the belittling and wore a hangdog expression even when he wasn’t around, you couldn’t be sure—could you?—whether her personality problems were the cause of her unhappy situation (the reason why she married this jerk and why she doesn’t leave him) or an effect (the result of all the belittling). In fact, you might blame her depression and passivity on her mother, who got her used to being belittled when she was a child. You would be wrong, but you would be admitting that she had these problems before she married the jerk.