If you haven’t read The Nurture Assumption by Judith Harris, you simply must. Years later, this paragraph is still with me:

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 wife?” and yet the situation is similar. I don’t expect that the way I acted toward my husband is going to determine what kind of person he will be ten or twenty years from now. I do expect, however, that it will affect how happy he is to live with me and whether we will still be good friends in ten or twenty years.

You could easily add that a great way to alienate your spouse is to try to change him. How’s that for an example of unintended consequences?