Another is learning how to communicate well. It's about listening, showing curiosity, ensuring you understand and validate your partner's feelings and, finally, showing empathy, Hendrix says. "If you know how to ski, you can ski the double black diamonds," he says. "If you don't know how, when you get that resistance to those moguls, you're going to fall."
Remember this, too: Conflict is a crucible for growth, Hunt says. And people need to coach each other about what they need—even after decades of life together. Hunt and Hendrix offer tips for couples, replete with cartoon-like illustrations, in their newest book, Making Marriage Simple, which comes out next month.
According to Robert Navarra, a San Francisco-based marriage and family therapist, the best long-term relationships are among couples who "treat each other like best friends, they're more positive with each other than negative, and they're very gentle in how they manage conflict." The stronger the friendship, the more likely a couple can resolve problems, which, in turn, strengthens the bond, he explains.
Navarra is certified and trains in the method of counseling taught by the Gottman Institute, a Seattle-based center for marriage therapy that draws heavily on research. According to the institute, following four behaviors—the so-called "four horsemen of the apocalypse"—will doom a marriage: criticism, defensiveness, contempt, and stonewalling. Navarra elaborates on these by prescribing their antidotes: In the first case, partners should express their needs without blaming each other; in the second, it's critical to accept at least some responsibility for a problem; and understanding and validation should replace contempt, which Navarra calls "the single biggest predictor of divorce." Stonewalling, or shutting down, most often affects men, who can recover from feeling overwhelmed by taking a 20-minute break from a troubling conversation.
Apart from that, people need to realize that a successful relationship must allow for and encourage the differences inherent in two unique people coming together. "Someone who can't tolerate those kinds of differences is asking you to not be who you are, and that's going to be a problem. You can't give up who you are for the sake of the relationship," Navarra says.
At its best, the relationship grows just as its partners do. And there's the real prize, say Hunt and Hendrix. "After you've been stretched, and you've got a partner who's worked with you, and you've worked with them," Hunt says, "there's not a feeling greater in the world than that one."