It's one of the great ironies of family life: If a married couple's relationship is rich and fulfilling, they are better able to deal with everyday stresses and strains. But if those same stresses overwhelm the couple, they may find themselves too tired to do the basic work to keep their relationship alive.

It's a vicious cycle -- and one faced by more and more couples in the '80s as they juggle jobs, housework and family, according to Denver-based author and parent educator Dolores Curran.

The scenario, as Curran describes it in her book Stress and the Healthy Family (Winston Press, 1985, $13.95), is all too familiar. Two-career couples may give their primary intimacy to their work, and their secondary intimacy to their children. They use ineffective ways to deal with everyday stresses -- things like budgeting their money, disciplining children, sharing housework and scheduling family activities. By week's end they are caught up in a whirlpool of demands -- too tired to work on their relationship, let alone make love.

"Having sex," one woman told Curran, "is like one more thing on the grocery list to cross off at bedtime."

In fact, a lack of interest in sex is the number one problem reported by sex therapists in clinics across the country, according to Carol Botwin, author of Is There Sex After Marriage? (Little, Brown, 1985, $16.95). And the only way to counter it is to make the sexual relationship a priority, she counsels. Husbands and wives should set aside time to be together, in settings that offer intimacy, romance and privacy.

Otherwise, they may survive the stresses of their day-to-day life -- only to wake up one day and realize they no longer can bridge the gulf that has grown between them.

To a certain extent, Botwin points out, a decline in sexual activity after marriage is normal and should be expected. Both authors describe a "couple life cycle" that goes through prescribed stages, such as courtship, birth of the first child, children's adolescence and empty nest. Each stage has a different effect on the couple's sexual relationship (the stage with the most profound effect: the birth of the first child), and drops or rises in sexual frequency are normal responses to the stresses of these stages.

It helps if the couple is in tune with the changes the other person is going through, says Curran. "We are not the same people we were when we married. As we get into each two or three more years of marriage, we change significantly. If the other person isn't aware of how we're changing in our attitudes and dreams, disappointments and behaviors, then that person cannot shift and grow."

Botwin and Curran agree that keeping the couple relationship alive and growing through various stages takes time and work. And they emphasize that the relationship should not take second place to work or children.

Among Curran's recommendations for alleviating stress and salvaging the marital relationship:

*Identify stresses. This may sound basic, but it is a critical first step: When a family realizes that things are out of control, they should stop and examine what the specific situations are that cause them trouble, so they can work together to find solutions.

*Communicate. "If there is one area to deal with in alleviating family stress, I would say couple communication," says Curran. This involves not only sharing of feelings, but also learning to resolve conflict -- an important part of communication.

In addition, the entire family must communicate. When things get too hectic and family members aren't getting along, they may realize they haven't had any fun together for a long time. They need to pull back, stop and renegotiate what's important to them. This may mean dropping unnecessary activities and setting aside one day just for fun.

*Identify strengths -- such as trust, respect, sharing responsibility well -- and use these strengths to deal with stresses.

*Plan time for husband and wife to be together. "Time is the one equalizer. We don't have the same amount of money, we don't have the same gifts and talents -- but we have the same amount of time. And families that deal well with time tend to prioritize activities better," says Curran.

This may mean cutting out activities for the kids or putting in less time at work. The two big thieves of couple time, says Curran, are work and children.

Setting aside a certain night each week for a "date" with your spouse can be invaluable. Without time alone, many couples find that their relationships eventually lose their vitality and die. Often they discover their marriage is no longer vital when the last child leaves homes.

One couple, says Curran, set aside Wednesday evenings as their night together to listen to music and talk. They didn't schedule anything else.

Another couple with a low budget for recreation -- $10 a week -- went to a movie every Saturday night. But they found that they still didn't have enough opportunity to talk to each other, "so they took their $10, and every night they hire a babysitter in the neighborhood who does the dishes and takes care of the children while they go for a long walk. Two dollars an evening."

"One of the best methods of foreplay," says Curran, "in spite of the sex manuals, is a long walk after dinner.

"You can live a long time on one night a week," she says. Don't try to make up for lost time with an annual vacation, she says: "Two weeks can't see you through the rest of the year."

In her book, Curran explores the special qualities of so-called "stress-reduced" or "stress effective" families, examining traits they consistently exhibit in dealing with everyday problems. She found that they:

*Expect stresses as normal, and not as evidence of their own failures.

*Have lower expectations and, especially in things like housekeeping standards, are able to live with a less-than-perfect life style.

*Tend to seek solutions. (Stressed families will find some way first of placing blame.)

*View stress as temporary, as opposed to others who see it as ongoing. This, says Curran, gives them more hope.

*Focus on the stresses that are controllable, and learn to live with the uncontrollable ones.

Curran's research showed discrepancies in how the husband and wife viewed the stresses in the same marriage. Money was listed as the highest stress for all groups surveyed. But for the married women, lack of shared responsibility in the family was the second-highest stress. This, says Curran, "didn't even appear on the men's list. This is a stress in itself."

For men, the second-highest stress was insufficient couple time, which, says Curran, "clearly says they miss that relationship they had with their wife, the one that brought them together.

"I don't think women understand this. I think if they knew that, they'd be a little more willing to say, 'I will give up some of the time I spend with children or on the home,' " says Curran. "And, really, it does mean that. It means you take it away from something else. Men have to give up some of the time they spend with work and so do women."

What is the future for the family? Curran has high hopes, she says, because she sees younger couples exhibiting different behavior from that of previous generations: people marrying later, being more frank with each other, sharing decision-making, having children later and sharing child-raising responsibilities.

And with these changes, the couple relationship is being recognized as the critical factor it is, says Curran, in solving all the other stresses the family encounters. Families possess real strengths. "We need to help families use these strengths," she says, "to deal with their stresses."