Love is mankind's most positive emotion. But it can also cause great pain for those who find themselves jilted, betrayed or abandoned. "Our whole culture is geared and meshed to help us fall in love, but nowhere are there signs to point the way out," concludes Debora Rothman Phillips, 39, an assistant clinical professor of psychiatry and sex therapist at Temple University Medical School in Philadelphia. Drawing on her experience in that post and at the Princeton Center for Behavioral Consultation, Phillips has set down guidelines on surviving the end of a marriage or an affair in her new book, How To Fall Out of Love (Houghton Mifflin, $6.95). Brooklyn-born Phillips lives in Princeton with her husband of 18 years, Bill, a research scientist at RCA Laboratories, and their two children, Ronald, 12, and Wendy, 5. Professor Phillips talked with Richard K. Rein of PEOPLE about love—falling out and then falling back in again.

How serious is falling out of love?

It can lead to depression and even suicide. If you lose someone to death, that's very painful. But we are talking about loss that is often coupled with brutal, overt rejection by someone we care about deeply. It can be worse than the death of a loved one.

Why is this so?

Because the two people are often living in the same community, possibly working in the same office, having to talk on the telephone or exchanging children if a divorce is involved. It's so easy to hope, "Gee, maybe someday it will all work out if I just do x, y and z." Those are usually false expectations.

Have you ever personally fallen out of love?

Yes, when I was 17.1 thought it was the end of the world, that this was the only person I could ever be in love with.

What causes people to fall out of love?

Sometimes the spark seems to go out for no reason. Sometimes we have an image of a person that the other partner can't really live up to. Maybe one person changes; the other does not. Reality may Just hit. The basic nitty-gritty gets in the way—dishes, garbage, children, taxes. They can destroy the romance.

Are people who lose at love natural-born losers?

No, some of the patients I see are among the most creative, successful, productive people I know. They're winners in American terms, but nothing—success, beauty, money, friends—seems to matter to them. They are in deep pain.

Are certain types more prone to be hurt in a love affair?

Absolutely not. It runs through every possible different personality. It's equally balanced between men and women, young and old, gay people as well as straight. It's being human that creates the pain.

Do spurned lovers try to hide the fact they have been rejected?

Men more so than women. Women talk endlessly about the fact that it's over and they are brokenhearted. Their friends get tired of hearing the same story again and again. Men have been taught not to show their feelings. It's not easy for most men to cry.

How do you begin to shake the painful obsession with a former lover?

It's an emotional relearning process. You learn to fall in love, and you can learn to fall out. You fall in love because he or she seems to fulfill a whole set of needs for you. A lot of it is magic and chemistry. There is intense physical attraction—a complex interplay of hormones, senses and emotions. You gloss over all the flaws.

What is the first step in unlearning love?

Stop thinking about that person. You can train a thought to stay away. You can starve a thought. Chances are you've already tried, and it hasn't worked. But thoughts can be stopped by a systematic program of behavior therapy. The purpose is not to shift the rejected lover's feeling to dislike or hate. I am aiming at the great middle ground of indifference.

What does this program require?

I ask people to make out a list of the best, most positive scenes and pleasures which do not involve the former lover. The list can include anything from being on a Greek island to making love outdoors with a complete stranger. It doesn't matter. The list is entirely their own, and nobody need see it.

What if memories of your old love return?

Now that you have your list, purposefully invite the former lover into your thoughts. But the first microsecond he or she enters your mind, yell as loudly as you can, "STOP!" In the next instant, bring in one of the most pleasurable thoughts from your list. That in essence is thought-stopping, actively inhibiting thoughts you want to go away.

Does it work?

Yes, but it is important to keep a record of how many times each day you think of the person you want to stop loving. One woman in her 50s, who had been left by a man 10 years younger, was thinking of him more than 100 times a day. After two days of shouting "Stop," out loud, she put a rubber band around her wrist that she could snap instead. In just over a week she was thinking of him only four times a day, but in other cases it may take as long as a month.

Can't you persuade people they really aren't in love?

Love is self-defined. If people tell me they're in love, I will accept it. And it also doesn't help to point out that the other person isn't really worthy of their love. That's being too rational at this point. They are feeling too unworthy themselves.

What else does help?

Falling out of love means thinking of that person not only less often but also in a different way. You have to view the person in life-size, not up on a pedestal. Silent ridicule is the way to change your response. Instead of seeing the lover romantically as you have in the past, imagine him or her in an absurd, ridiculous scene.

How does one go about silent ridicule?

The important point is to be sure your scene is based on a real foible or flaw or exaggeration of personality. One woman imagined her ex-lover, a natty dresser, wearing a homburg several sizes too large. A young man of 30, who was tantalized by the smile of another man's wife, made himself think of her with no teeth. Imagine a man at a board meeting wearing diapers. Have a good laugh. Being able to laugh at your predicament is the most important indicator of good emotional health.

What about one's own self-esteem?

Rejection makes you depressed. So build a positive self-image and increase your self-assertiveness. One image-building technique that's helpful is to write down, every day, at least two positive things about yourself. They can be as trivial as putting the cap back on the toothpaste tube. Be generous. Praise yourself.

What is the cure if jealousy won't go away?

Thought-stopping is helpful, combined with a technique I have been teaching for almost four years, and it works. I call it graduated calming. It requires learning deep muscle relaxation until anxiety subsides. Then by degrees you imagine scenes that usually cause anxiety. With practice you can become indifferent to what used to make you most jealous.

What if, after all this, one is still physically attracted to an ex-love?

There is an ugly technique called repulsion—a radical means of breaking the power of physical attraction. It teaches you to associate physical contact with that person with anything you find totally repulsive—excrement, vomit, pus—and the smellier, slimier and nastier the better. One of the most vivid I've heard is "ooze from a dead rat." Happily, it's a technique that's rarely needed.

As the old love loses its spell, what about new love?

You may feel you will never fall in love again. And who knows, you may be right. But the odds are against your staying out of love. For one thing, you're wiser now.

What advice would you offer?

Your experience with a new person is like falling in love for the first time. You have to learn again. If you bring an old lovemaking agenda to a new person, it is going to get in the way. So please, take your time.

What effect does being a sex therapist have on your own love life?

If it teaches anything, it is never to focus on performance. The most important thing we can learn is that sex is not an achievement, but a pleasure. If anyone keeps score, it certainly shouldn't be a sex therapist. We know the casualty rate from doing that.