How to have a successful marriage that lasts, according to relationship experts who married each other

• We interviewed four couples in which both partners are relationship experts about their best marriage advice.
• Common themes emerged, including: Stay curious about your partner, and know the whole is greater than the sum of its parts.
• Ultimately, marriage is hard for everyone, but there are some time-tested tricks to make it easier.

There's a curious trend among relationship experts: Many of them are married. To each other.

When I first realized this, it sounded to me like the makings of either heaven or hell.

Case for heaven: No one ever name-calls, or violates their partner's trust, or shuts down emotionally because you both know those are counterproductive behaviors. Case for hell: You can't storm off like a child during an argument about chores because you just counseled a client not to do that this morning.

Curious to know which way the pendulum swings, I called up four married couples in which both partners are relationship experts and asked whether and how they practice what they preach.

In the four conversations, I heard some common themes about the conflicts that have played out in their marriages and how they've used their knowledge of successful relationships to resolve them.

Read on to find out how the pros do marriage - and what can you learn from them.