“O, beware… of jealousy; it is the green-eyed monster,” wrote William Shakespeare in the 16th century. In 400 years, we don’t seem to have been able to tame or conquer this monster. Nothing will harm your relationship more than jealousy, suspicion or mistrust. Especially when you are apart, you need to find a way to trust each other. When you are not together, your imagination can run wild and make it even more of a problem.

What happens when one of you becomes jealous? Most jealousy is not based on any real betrayal. Usually, it is a fearful fantasy of what might happen. Jealousy involves various combinations of fear, suspicion, envy, rage, competitive failure, humiliation, grief, self-contempt, betrayal and abandonment. Sigmund Freud thought jealousy was a delusion rising from excessive dependence and lack of self-esteem.

Jealousy is often based on insecure feelings of wanting to own the other person and not allow him or her to fill different needs with different people; but because we can’t be everything to each other, most jealousy is illogical and unrealistic.

It’s insulting to yourself and to your partner, because when you’re jealous, you’re thinking that someone else is more attractive to your partner than you are, and that your partner is not loyal. Jealousy is usually less about your partner’s behavior than it is about what you’re afraid the behavior means. Jealousy can lead to upsetting arguments, tears, resentment and accusations, even when no actual infidelity exists.

You can be fearful, self-protective and jealous as a result of being hurt in a previous relationship acting as if you believe your partner will hurt you the same way you were hurt by someone else.

Here are some steps you can use to overcome jealousy in your relationship:

Step 1. Discuss your jealous feelings, if you have them.

Where do they come from? Have you been betrayed or abandoned before? Perhaps it was by a previous partner? Or possibly it was a family member? Did something trigger your jealous thoughts this time? Does your partner sometimes have jealous feelings, too? Be willing to open up about how you feel, and to hear how your partner feels. You can’t reach a mutually satisfactory result if you don’t tell the truth or listen to your partner.

Step 2. Make some rules about behavior when you’re apart.

Is it OK to go to lunch with a member of the opposite sex? What about dinner? Can you work out together or work on projects at night? What if the other person is married? Make sure you and your partner feel comfortable with your agreements: Once you have a list you can live with, promise to abide by it; as long as you’re willing to keep your promise. Later, when you both feel more secure, you may be able to relax the limits. Don’t push too hard, demand the impossible, or risk too much, because you’ll frighten each other. Keep in mind that jealousy breaks down trust. If you begin to be upset, talk about it and encourage your partner to do the same.

Step 3. Make changes together.

If you want to change your agreements, talk about any changes before you act on them, and keep each other up to date. Lying to your partner about whether you broke the rules is far more damaging than whatever you did. If you make a mistake, confess it, and offer some kind of plan to fix the problem. If it’s your partner who goofed, hear what he or she has to say before blaming or getting upset. Be willing to talk about it, and give yourselves a chance to solve the problem. If either of you cannot behave within your agreements, or cannot keep your jealousy within bounds, then get professional counseling to avoid creating a marital disaster.

Step 4. Cultivate patience.

If you take your time and keep your communication open, the trust between you will grow. You’ll eventually figure out that both of you are doing your best to stay within the bounds. As you learn and grow together, your trust will gradually build; and as it grows stronger, you can begin to relax the rules and allow yourselves more flexibility and freedom.

Step 5. Be gentle with each other.

Do your best not to get angry at each other for being jealous. Resist punishing or controlling your partner, especially if he or she hasn’t really broken any mutual agreements. If one of you misunderstood and is jealous for no reason, be willing to apologize and reassure each other of your love and faithfulness. You’ll have much better luck if you remain calm, and work it out together.

— Tina Tessina, Ph.D., has been a licensed California psychotherapist for more than 30 years.