Breakable Rule #1: Use "I" statements, not "you" statements, when talking about a complaint.

Sticking to emotion-focused "I" statements rather than accusatory "you" statements ("I feel upset" rather than "You make me so mad") has helped couples communicate more clearly and calmly for decades now. But there's a third option that may be even better, a 2009 study found: "we" statements, like "We need to find time" or "We should give it a shot." When longtime couples were discussing a sticking point in their relationship, those who used more "we" words (we, us, ours, and so on) acted more positively toward each other, showed fewer physical signs of stress, and were happier in their marriages overall. "You can use your language as an indicator of the current state of your relationship, like a gas gauge on your car," says Robert Levenson, a social psychologist at the University of California, Berkeley, who co-authored the study: Lots of "we" words and you're likely doing well enough to make it a long way; almost none and you may be running on fumes.

Breakable Rule #2: Never go to bed angry.

Half a dozen psychologists and therapists said they'd toss out this rule. Some problems simply can't be fixed in the 120 minutes between tucking in the kids and turning in yourselves. Sleeping on an argument can help both parties come at it refreshed later on—which isn't to say that you should lie in bed mentally gathering ammunition for your next attack. Psychotherapist Linda Young suggests concentrating on one of the best days you and your partner have spent together while you're falling asleep. If you're too angry for that, focus on any pleasant thought (as long as it's not about that old boyfriend from college).