Book: My Secret Garden by Nancy FridayPower—or powerlessness—is usually what leads people to withhold sex or give out sex at their discretion. Some may want total control. Others find it is the only sense of control they have. Most times, a withdrawal from sex is only the tip of a problem.

"Power struggles are a normal part of every relationship," says Lonnie Barbach, a San Francisco therapist and co-author of Going the Distance: Finding and Keeping Life-long Love. "But if you feel a lack of sexual desire, it means you've gotten to a secondary stage, and it's usually something that needs to be dealt with."

When Sex Is Not Pleasurable

According to the Masters and Johnson Institute in St. Louis, Missouri, some couples do have problems of inhibited sexual desire. Sex is naturally a pleasure, says Institute Director Mark Schwartz. People should not force themselves to feel sexual any more than they should force themselves to enjoy a hot fudge sundae. "Never 'service' your partner out of a sense of duty or guilt," says Schwartz. It is important for each person's needs to be respected. "All human beings are in a process of growth," he says. "A relationship based on the role of the woman as an object cannot last."

Today, very few people question anyone's right to decline sex, even in marriage. But, couples should be aware that when one partner has begun to withhold sex or give in to sex as a duty, there is something amiss in the relationship that must be addressed.

What to Do?

Even if sexual ploys garner the desired attention or win some other battle, the real problems go unsolved. Feelings of disappointment, anger, and frustration begin to take over. Sex, which should be enjoyable on a physical, emotional, and even spiritual level, is degraded.

For those who are tempted to use sex, it is important to stop and ask why. In many cases, couples will benefit from therapy to help them repair the relationship. This can be a good opportunity to work out unresolved issues. Many people will find that power struggles or definitions of roles from their own families are cropping up in the relationship. Schwartz adds that through therapy "couples can really transform their relationship, especially if they start early enough."