Long live the new marriage! We once prized the institution for the practical pairing of a cash-producing father and a home-building mother. Now we want it all—a partner who reflects our taste and status, who sees us for who we are, who loves us for all the "right" reasons, who helps us become the person we want to be. We've done away with a rigid social order, adopting instead an even more onerous obligation: the mandate to find a perfect match. Anything short of this ideal prompts us to ask: Is this all there is? Am I as happy as I should be? Could there be somebody out there who's better for me? As often as not, we answer yes to that last question and fall victim to our own great expectations.

That somebody is, of course, our soul mate, the man or woman who will counter our weaknesses, amplify our strengths and provide the unflagging support and respect that is the essence of a contemporary relationship. The reality is that few marriages or partnerships consistently live up to this ideal. The result is a commitment limbo, in which we care deeply for our partner but keep one stealthy foot out the door of our hearts. In so doing, we subject the relationship to constant review: Would I be happier, smarter, a better person with someone else? It's a painful modern quandary. "Nothing has produced more unhappiness than the concept of the soul mate," says Atlanta psychiatrist Frank Pittman.

Consider Jeremy, a social worker who married a businesswoman in his early twenties. He met another woman, a psychologist, at age 29, and after two agonizing years, left his wife for her. But it didn't work out—after four years of cohabitation, and her escalating pleas to marry, he walked out on her, as well. Jeremy now realizes that the relationship with his wife was solid and workable but thinks he couldn't have seen that 10 years ago, when he left her. "There was always someone better around the corner—and the safety and security of marriage morphed into boredom and stasis. The allure of willing and exciting females was too hard to resist," he admits. Now 42 and still single, Jeremy acknowledges, "I hurt others, and I hurt myself."

Like Jeremy, many of us either dodge the decision to commit or commit without fully relinquishing the right to keep looking—opting for an arrangement psychotherapist Terrence Real terms "stable ambiguity." "You park on the border of the relationship, so you're in it but not of it," he says. There are a million ways to do that: You can be in a relationship but not be sure it's really the right one, have an eye open for a better deal or something on the side, choose someone impossible or far away.

Yet commitment and marriage offer real physical and financial rewards. Touting the benefits of marriage may sound like conservative policy rhetoric, but nonpartisan sociological research backs it up: Committed partners have it all over singles, at least on average. Married people are more financially stable, according to Linda Waite, a sociologist at the University of Chicago and a coauthor of The Case for Marriage: Why Married People are Happier, Healthier and Better Off. Both married men and married women have more assets on average than singles; for women, the differential is huge.

The benefits go beyond the piggy bank. Married people, particularly men, tend to live longer than people who aren't married. Couples also live better: When people expect to stay together, says Waite, they pool their resources, increasing their individual standard of living. They also pool their expertise—in cooking, say, or financial . In general, women improve men's health by putting a stop to stupid bachelor tricks and bugging their husbands to exercise and eat their vegetables. Plus, people who aren't comparing their partners to someone else in bed have less trouble performing and are more emotionally satisfied with . The relationship doesn't have to be wonderful for life to get better, says Waite: The statistics hold true for mediocre marriages as well as for passionate ones.

The pragmatic benefits of partnership used to be foremost in our minds. The idea of marriage as a vehicle for self-fulfillment and is relatively new, says Paul Amato, professor of sociology, demography and family studies at Penn State University. Surveys of high school and college students 50 or 60 years ago found that most wanted to get married in order to have children or own a home. Now, most report that they plan to get married for love. This increased emphasis on emotional fulfillment within marriage leaves couples ill-prepared for the realities they will probably face.

Because the early phase of a relationship is marked by excitement and idealization, "many romantic, passionate couples expect to have that excitement forever," says Barry McCarthy, a clinical psychologist and coauthor—with his wife, Emily McCarthy—of Getting It Right the First Time: How to Build a Healthy Marriage. Longing for the charged energy of the early days, people look elsewhere or split up.

Flagging passion is often interpreted as the death knell of a relationship. You begin to wonder whether you're really right for each other after all. You're comfortable together, but you don't really connect the way you used to. Wouldn't it be more honest—and braver—to just admit that it's not working and call it off? "People are made to feel that remaining in a marriage that doesn't make you blissfully happy is an act of existential cowardice," says Joshua Coleman, a San Francisco psychologist.

Coleman says that the constant cultural pressure to have it all—a great sex life, a wonderful family—has made people ashamed of their less-than-perfect relationships and question whether such unions are worth hanging on to. Feelings of dissatisfaction or disappointment are natural, but they can seem intolerable when standards are sky-high. "It's a recent historical event that people expect to get so much from individual partners," says Coleman, author of Imperfect Harmony, in which he advises couples in lackluster marriages to stick it out—especially if they have kids. "There's an enormous amount of pressure on marriages to live up to an unrealistic ideal."

Michaela, 28, was drawn to Bernardo, 30, in part because of their differences: She'd grown up in European boarding schools, he fought his way out of a New York City ghetto. "Our backgrounds made us more interesting to each other," says Michaela. "I was a spoiled brat, and he'd been supporting himself from the age of 14, which I admired." Their first two years of marriage were rewarding, but their fights took a toll. "I felt that because he hadn't grown up in a normal family, he didn't grasp basic issues of courtesy and accountability," says Michaela. They were temperamental opposites: He was a screamer, and she was a sulker. She recalls, "After we fought, I needed to be drawn out of my corner, but he took that to mean that I was a cold bitch." Michaela reluctantly concluded that the two were incompatible.

In fact, argue psychologists and marital advocates, there's no such thing as true compatibility. "Marriage is a disagreement machine," says Diane Sollee, founder of the Coalition for Marriage, Family and Couples . "All couples disagree about all the same things. We have a highly romanticized notion that if we were with the right person, we wouldn't fight." Discord springs eternal over money, kids, sex and leisure time, but psychologist has shown that long-term, happily married couples disagree about these things just as much as couples who divorce.

"There is a mythology of 'the wrong person,'" agrees Pittman. "All marriages are incompatible. All marriages are between people from different families, people who have a different view of things. The magic is to develop binocular vision, to see life through your partner's eyes as well as through your own."

This same respect for our own needs spurred the divorce-law reforms of the 1960s and 1970s. During that era, "The culture shifted to emphasize individual satisfaction, and marriage was part of that," explains Paul Amato, who has followed more than 2,000 families for 20 years in a long-term study of marriage and divorce. Amato says that this shift did some good by freeing people from abusive and intolerable marriages. But it had an unintended side effect: encouraging people to abandon relationships that may be worth salvaging. In a society hell-bent on individual achievement and autonomy, working on a difficult relationship may get short shrift, says psychiatrist Peter Kramer, author of Should You Leave?

"So much of what we learn has to do with the self, the ego, rather than giving over the self to things like a relationship," Kramer says. In our competitive world, we're rewarded for our individual achievements rather than for how we help others. We value independence over , and sacrifices for values like loyalty and continuity seem foolish. "I think we get the divorce rate that we deserve as a culture."

The steadfast focus on our own potential may turn a partner into an accessory in the quest for self-actualization, says Maggie Robbins, a therapist in New York City. "We think that this person should reflect the beauty and perfection that is the inner me—or, more often, that this person should compensate for the yuckiness and mess that is the inner me," says Robbins. "This is what makes you tell your wife, 'Lose some weight—you're making me look bad,' not 'Lose some weight, you're at risk for diabetes.'"

Michaela was consistently embarrassed by Bernardo's behavior when they were among friends. "He'd become sullen and withdrawn—he had a shifty way of looking off to the side when he didn't want to talk. I felt like it reflected badly on me," she admits. Michaela left him and is now a wealthy entrepreneur. "I just thought there had to be someone else out there for me."

The urge to find a soul mate is not fueled just by notions of romantic manifest destiny. Trends in the workforce and in the media create a sense of limitless romantic possibility. According to Scott South, a demographer at SUNY-Albany, proximity to potential partners has a powerful effect on relationships. South and his colleagues found higher divorce rates among people living in communities or working in professions where they encounter lots of potential partners—people who match them in age, race and education level. "These results hold true not just for unhappy marriages but also for happy ones," says South.

The temptations aren't always living, breathing people. According to research by psychologists Sara Gutierres and Douglas Kenrick, both of Arizona State University, we find reasonably attractive people less appealing when we've just seen a hunk or a hottie—and we're bombarded daily by images of gorgeous models and actors. When we watch Lord of the Rings, Viggo Mortensen's kingly mien and Liv Tyler's elfin charm can make our husbands and wives look all too schlumpy.

Kramer sees a similar pull in the narratives that surround us. "The number of stories that tell us about other lives we could lead—in magazine articles, television shows, books—has increased enormously. We have an enormous reservoir of possibilities," says Kramer.

And these possibilities can drive us to despair. Too many choices have been shown to stymie consumers, and an array of alternative mates is no exception. In an era when marriages were difficult to dissolve, couples rated their marriages as more satisfying than do today's couples, for whom divorce is a clear option, according to the National Opinion Research Center at the University of Chicago.

While we expect marriage to be "happily ever after," the truth is that for most people, neither marriage nor divorce seem to have a decisive impact on happiness. Although Waite's research shows that married people are happier than their single counterparts, other studies have found that after a couple years of marriage, people are just about as happy (or unhappy) as they were before settling down. And assuming that marriage will automatically provide contentment is itself a surefire recipe for misery.

"Marriage is not supposed to make you happy. It is supposed to make you married," says Pittman. "When you are all the way in your marriage, you are free to do useful things, become a better person." A committed relationship allows you to drop pretenses and seductions, expose your weaknesses, be yourself—and know that you will be loved, warts and all. "A real relationship is the collision of my humanity and yours, in all its joy and limitations," says Real. "How partners handle that collision is what determines the quality of their relationship."

Such a down-to-earth view of marriage is hardly romantic, but that doesn't mean it's not profound: An authentic relationship with another person, says Pittman, is "one of the first steps toward connecting with the human condition—which is necessary if you're going to become fulfilled as a human being." If we accept these humble terms, the quest for a soul mate might just be a noble pursuit after all.