You have a friend of the opposite sex who really understands you. The two of you can talk about anything, and you do. ‘We’re just friends,’ you tell yourself​—although your spouse might think otherwise if he or she were privy to your lingering conversations.

Likely, your friendship is already too close and you need to address the situation. First, though, consider why you might have become entangled in such a relationship.

Fulfillment. Simply put, attention from the opposite sex feels good. It flatters us to know that we are valued, and it makes us feel attractive. After being married for a time, you might begin to find reassurance in the company of a friend of the opposite sex. But know this: Having such needs fulfilled by someone other than your spouse comes at a cost. When you form an improper emotional connection with a member of the opposite sex, you weaken your connection with your spouse. In a sense, you rob your spouse of the affection you owe him or her.

• Ask yourself, ‘What needs are being fulfilled by this friendship that would better be fulfilled in my marriage?’

Vulnerability. The Bible acknowledges that those who marry will have a degree of “tribulation.” (1 Corinthians 7:28) For instance, at times you might feel neglected or unappreciated by your spouse, or you may harbor resentment over an unresolved conflict. Perhaps your spouse avoids talking about such issues, leaving you frustrated and vulnerable to the attention of someone else. Some experts say that shying away from discussing difficult issues can be a significant predictor of unhappiness in marriage​—and even a predictor of divorce.

• Ask yourself, ‘Is there a void in my marriage that has made me vulnerable to an inappropriate friendship?’

Recognize the danger. The Bible says: “Can you carry fire against your chest without burning your clothes?” (Proverbs 6:27, Good News Translation) The fact is, developing a romantic attachment when you are already married to someone else is destructive. (James 1:14, 15) It is not just a matter of what might occur. Consider what has already happened. By giving that kind of attention to someone else, you have robbed your spouse of the attention he or she should get from you.

Give up the illusion. A close friendship might make you wonder what life might have been like had you married this person. Likely, though, you are pitting your friend’s strengths against your spouse’s weaknesses​—an unfair comparison, to say the least! Remember, too, that the euphoria you experience when you think about your friend is probably the same feeling you initially had for the person you married.​—Bible principle: Jeremiah 17:9.

Set boundaries. People will install an alarm system in their vehicle or home to prevent theft. You can do something similar for your marriage. “Safeguard your heart,” says the Bible. (Proverbs 4:23) How can you do that? Try the following:

• Send out clear signals that you are already committed​—perhaps by keeping photographs of your spouse at work.​—Bible principle: Genesis 2:24.

• Decide what you will and will not tolerate when it comes to conduct with the opposite sex. For example, it would hardly be fitting to talk to such a friend about your marital problems or to go out for drinks with a coworker of the opposite sex.

• If you have become too close to a member of the opposite sex, end the relationship. If that seems too much to bear, ask yourself why. Instead of trying to defend your relationship with this person, stand up for your spouse and take steps to protect your marriage.​—Bible principle: Proverbs 5:18, 19.