10 Unspoken Marriage Rules

10. Be each other's number one.

In other words, be wary of outsider influence, like a friend putting relationship-threatening ideas in your head or work or hobbies competing for your attention. "Happy couples have just as much conflict as those who divorce, but they know ways to get through it," says Dr. Castaldo. "A couple has to have a strong boundary around themselves and they can't allow anybody to get in between."