High school chemistry taught me a very valuable lesson: When certain substances come into close contact, they can form a chemical reaction. I proved that one day during my senior year of high school when I dropped a jar full of pure sodium off a bridge into a river and nearly blew up the bridge!

Order Avoiding the Greener Grass Syndrome by Nancy C. Anderson

What I've learned since then is that many people don't respect the laws of chemistry any more than I did as a teenager. They mix volatile ingredients without giving much thought to the consequences. I've discovered that many married people don't understand that a chemical reaction can occur with someone other than their mates.

Don't misunderstand me—I'm not just talking about sexual attraction. I'm referring to a reaction of two hearts, the chemistry of two souls.

This is emotional adultery—an intimacy with the opposite sex outside of marriage. Emotional adultery is unfaithfulness of the heart. When two people begin talking of intimate struggles, doubts or feelings, they may be sharing their souls in a way that God intended exclusively for the marriage relationship. Emotional adultery is friendship with the opposite sex that has progressed too far.

I have looked into the eyes of many men and women who have fallen into full-fledged adultery, and what I saw made me nauseous. As I've talked with them, I've discovered that, in most cases, the adulterous relationships started as a casual relationship at work, school, even church.

A husband talks with a female co-worker over coffee and shares some struggles he's experiencing with his wife or kids. She tells of similar problems, and soon the emotions ricochet so rapidly that their hearts ignite and ultimately become fused as one. To those who have experienced it, this bonding seems too real to deny.

You may be converging on a chemical reaction with another person when:

• You've got a need you feel your mate isn't meeting—a need for attention, approval, or affection.
• You find it easier to unwind with someone other than your spouse by dissecting the day's difficulties over lunch, coffee, a ride home…or through E-mail correspondence on the Internet.
• You begin to talk about problems you're having with your spouse.
• You rationalize the "rightness" of this relationship by saying that surely it must be God's will to talk openly and honestly with a fellow Christian.
• You look forward to being with this person.
• You wonder what you'd do if you didn't have this friend to talk with.
• You hide the relationship from your mate.

When you find yourself connecting with another person as a substitute, you've started traveling a road that ends too often in adultery and divorce. But how do you protect yourself to keep this from occurring?

First, know your boundaries. Put fences around your heart to protect sacred ground, reserved only for your spouse. Barbara and I are careful to share our deepest feelings, needs, and difficulties only with each other.

Second, realize the power of your eyes. As it has been said, your eyes are the windows to your soul. Pull the shades down if you sense someone is pausing a little too long in front of your windows.

I realize that good eye contact is necessary for effective conversation, but there's a deep type of look that must be reserved for your spouse. Frankly, I don't trust myself.

Some women may think I'm insecure because I don't hold eye contact very long, but I don't trust my sinful nature. I've seen what has happened to others, and I know it could happen to me.

Third, extinguish chemical reactions that have already begun. If a friendship with the opposite sex meets needs that only your mate should be meeting, end it quickly. To stop a chemical reaction, one of the elements must be removed. It may be a painful loss at first, but it isn't nearly as painful as temptation that has given birth to sin.

Years ago, Ruth Senter wrote an incredibly candid article about her friendship with a Christian man she met in a graduate school class. Her struggle and godly response to this temptation were graphically etched in a letter that ended the relationship: "Friendship is always going somewhere unless it's dead," she wrote. "You and I both know where ours is going. When a relationship threatens the stability of commitments we've made to the people we value the most, it can no longer be."

Fourth, beware of isolation in your marriage. One strategy of the enemy is to isolate you from your spouse, especially by tempting you to keep secrets from your mate. Barbara and I both realize the danger of isolation to our marriage. We work hard at bringing things out into the open and discussing them.

Finally, never stop courting your mate. One of the most liberating thoughts I've ever had in my marriage relationship is that I will never stop competing for Barbara's love. As a result of that commitment, I stay much more creative in how I communicate with her emotionally and sexually.

I am well aware that if I start taking her for granted, someone else could walk into her life and catch her at a weak point. My constant goal is to strengthen her and let her know that she is still the woman I decided to carry off to the castle in 1972.

Many people who commit adultery express surprise that it happened; they talk as if they were carried along by an irresistible force of nature. But remember that nobody falls off a cliff if they're standing 40 feet away. Instead, they inch closer and closer to the abyss until they find themselves in danger.

You need to make your marriage relationship such a priority that you don't come anywhere near the edge.