"Pay attention to the age of the relationship rather than the age of the people," said Dr. Sheryl Kingsberg, chief of the division of behavioral medicine in the department of obstetrics and gynecology at Case Western Reserve University School of Medicine. "How long has the relationship gone on?"
In the earliest stages, every relationship has the "unfair advantage" of a high level of passion, according to Kingsberg. Experts even have a word for it – limerence. But that period of intense infatuation eventually ends, usually after anywhere from six months to two years.
"The couple, at that point, is at a crossroads," said Kingsberg. "Either they move into more of a partnership and build a life together or they break up and move on."
Half of all American marriages will end in divorce, but for the millions of couples who stick with it, life can be full of challenges.
Women face numerous hurdles, from making time for intimacy amid a busy family life to maintaining good communication skills. Some worry about the heartbreak of infidelity and other women complain that they are no longer attracted to a mate because he has put on extra pounds.
"Successful couples, those who really are the happiest, know that they have to work at it," she said. "Couples who expect it will happen automatically and take each other for granted, at high risk for failing."
Ann Rosen Spector, a clinical psychologist from Philadelphia who specializes in couples therapy, said, "When the relationship isn't doing well, you don't feel good about yourself."
"Relationships are always a work in progress so when we start to take it for granted, and don't put in as much attention and care, it's not going to thrive," she said. "One of the biggest hurdles is complacency."
KIngsberg and Spector both say women are more stressed today than ever before, juggling the demands of careers and motherhood. It's easy to lose focus and put an important relationship on the back burner.
"Make time for each other and talk about issues, small, medium and large," said Spector. "Carve out time, a small amount each day. Try to build the 'we' and not always look at the 'me.'"
Take time to listen to the partner and choose the argumentative battles. "I tell couples if they are fighting about this now, do they want to be fighting about it in 30 years?" she said. "People say, 'no.' They need to take the long view. This is an investment."