Here's an excellent summary:

1. The four things that kill relationships: Criticism, Defensiveness, Contempt and Stonewalling.
2. The three things that prevent them: Know your partner, respond positively to “bids” and admire your partner.
3. The best predictor of relationship success is how you and your partner tell your “story of us.”
4. The beginning of the conversation is crucial. Negativity compounds. Keep a cool head and resist emotional inertia.

One last thing that really blew me away: what makes for happy relationships sounds a lot like what makes for happiness in general.

Research shows, happy people seek out the positive and are grateful for it. Unhappy people find the negative in everything.

There’s a very similar dynamic in relationships: Masters scan their relationship for good things, disasters are always noting the bad.

And not only that—the Masters’ way of looking at the world is actually more accurate. Here’s John:

People who have this negative habit of mind miss 50 percent of the positivity that outside objective observers see. So the positive habit of mind is actually more accurate. If you have a negative habit of mind, you actually distort toward the negative and you don’t see the positive. People with the positive habit of mind, it’s not that they don’t see the negative—they do, they see it—but they really emphasize the positive in terms of the impact on them. That’s the difference.