Jealousy has often been called the "green-eyed monster," and with good reason. The "monster" is fueled by envy and can over time devour the trust and harmony in a relationship.

According to B.C. Forbes, "Jealousy...is a mental cancer." It spreads quickly and can be fatal to a marriage. Once it gets a foothold, the jealous spouse becomes even more jealous, often over insignificant things. Comedian Rodney Dangerfield captures what happens in these remarks: "My wife's jealousy is getting ridiculous. The other day she looked at my calendar and wanted to know who May was."

You're more prone to jealousy and envy when you are feeling insecure and fearful. Several years into my first marriage, I remember feeling unusually jealous of a woman that my husband worked with. The co-worker had dark, sultry looks, long flowing hair, and a figure that drove males wild. As if that wasn't enough, she was also funny and outgoing, with great communication and social skills. At office parties, the husbands could be found circled around her, competing for her attention.

At the time, I was too embarrassed to tell my husband that I had been ambushed by such intense envy. Eventually, the co-worker moved on to another company, but I still vividly remember how much I wanted to be like her and how depressed I felt each time I compared my attributes to hers.

"To cure jealousy is to see it for what it is, a dissatisfaction with self," states Joan Didion. Jealousy brings out the worst in us and causes us to resent someone else for having what we think we don't have-looks, charm, money, prestige, romance, charisma, success. When we're jealous, whatever measuring stick we use makes us feel lacking and "less than."

Fear is also involved when we feel jealous-fear that we'll never have what the other person has, fear that we're not as good as someone else, fear of losing our spouse to another, fear that we're not attractive or desired, and fear of being ridiculed. Joseph Addison defines jealousy as "...that pain which a man feels from the apprehension that he is not equally beloved by the person whom he entirely loves." When we're jealous, we feel insecure and lack self-esteem.

A counseling client once shared that he was being torn apart by jealousy. Whenever his wife was even a few minutes late, he visualized her stopping to flirt with someone in the grocery store or became convinced that she was using the time to secretly call another man. His rational mind knew that there was nothing to base these anxieties on, that his wife loved him and had never betrayed his trust. But he was unable to stop his "worst scenario" fantasies.

As we dug deeper into his past experiences, it turned out that his first long-term girlfriend in college had secretly cheated on him with a close friend of his. Thus, he was transferring his fears from the previous experience onto his wife. He became extremely jealous and afraid that he was going to lose her in the same way. Ironically, the marriage had become so unbearable for his wife that she did eventually turn her affections toward someone else. The client's inability to control his jealousy brought about the very thing he was afraid would happen. By the time he finally came for counseling, his obsessive jealousy had already killed the marriage.

For a marriage to be healthy, there has to be trust, and jealousy undermines that trust. The following seven tips can help you to keep jealousy from undermining your relationship with your spouse:

1. When you first notice that you're feeling jealous, immediately try to identify what insecurity or fear is being triggered. Is it a fear of abandonment? A fear that you don't measure up? Your own insecurities about not feeling successful or attractive enough? When insecurities or fears are activated, you're more likely to overreact in a way that could hurt your relationship.

2. Instead of focusing on the behavior that you want your spouse to stop so that you won't feel the uncomfortable pangs of jealousy, examine your self-talk. Are you telling yourself, "My wife shouldn't be flirting with him like that," or "My husband will probably leave me for someone else one day"? You can change how you feel by changing what you tell yourself about the situation.

3. Take a close look at your past history. Did one of your parents cheat on the other one? Did a spouse in your first marriage betray you? Or did you cheat on a partner in the past? If so, it is likely that you are projecting your past experiences and feelings on to your present spouse. Try to keep the past separate from the present.

4. Do a reality check. Instead of getting upset about the future scenario your mind has jumped to, list what exact behaviors you're upset about. Your list might read, "My wife talked to a handsome bachelor that she had just met when we were at our friend's party. She smiled and laughed and looked like she was having a good time." So the objective list of behaviors includes talking, smiling, laughing, and looking like she was having a good time-not exactly unusual party behavior.

5. Stay rooted in the present moment, and reel in your imagination before it runs away with you. You don't want to damage your relationship by accusing your spouse of something he or she didn't do. Besides harming the trust and harmony of your marriage, if you routinely accuse your spouse of imaginary transgressions, you could end up pushing him or her into the very behavior you're zeroing in on.

6. Think before you speak. Notice the difference in the two following approaches: A) "I felt neglected last night at the party when you never spent any time with me. In fact, if I'm really honest, I was starting to feel slightly jealous, and I don't like that feeling. I really need to talk about this with you." or B) "I am so sick of you always flirting with every man in sight when we go to a party. People are going to think you're nothing but a tramp." Think about which approach will be most likely to result in a meaningful discussion.

7. Remind yourself that your spouse chose you, so he or she finds you and your qualities attractive. Also remember that confidence and self-respect is attractive to others. When you throw a jealous fit, you appear insecure and needy, as if you need constant reassurance of your spouse's commitment. Repeat to yourself, "My wife (or husband) loves me and chose me to spend her life with. I'm lucky to have such a personable, attractive spouse who loves me."

Nancy J. Wasson, Ph.D., is co-author of Keep Your Marriage: What to Do When Your Spouse Says "I don't love you anymore!" This is available at http://www.KeepYourMarriage.com, where you can also sign up for the free weekly Keep Your Marriage Internet Magazine to get ideas and support for improving your marriage.