Several years ago, I posted this "viral" post on my Facebook page. I had no idea how much conversation and controversy I was about to stir up when I posted the following words...

_Be VERY careful about having close friends of the opposite sex. Most affairs start out as "friendships" that cross the line. Never give a friend or co-worker of the opposite sex time and attention that rightfully belongs to your spouse. Your spouse should be your best friend, so always protect your marriage._

Those few short sentences caused a firestorm of support, scorn and debate. Some people chimed in and said things like, "Well, some of my best friends are of the opposite sex and my spouse has no problem with it," and others would quickly jump in and say, "You're harming your marriage and not even realizing it. My marriage ended because of a "friendship" I thought was harmless."

In the years since first posting this, I believe the truth behind it more than ever for the reasons I will list below. When I've unpacked my reasoning to co-workers and groups of friends, two of my most vocal critics were ladies who were co-workers at the time. They both passionately disagreed with my reasoning and insisted that a married person could and should have intimate friendships with people of the opposite sex. Ironically, in the time since they first expressed their disagreement, one of those women has left her husband for another woman and is now living in a lesbian relationship. The other woman had an affair with a close family "friend" and is now trying to repair her marriage and win back the trust of her heartbroken husband.

As a quick disclaimer, when I'm referring to a "close friend" of the opposite sex, I'm NOT talking about friends or colleagues whom you regularly see socially in group settings or have occasional conversations one-on-one. I'm certainly not saying you should cut of all contact with the opposite sex and life in some kind of monastery of isolation. I'm referring specifically to being cautious about a "friend" with whom you have consistent, one-on-one contact and intimate details of your life are shared. I believe this type of "friendship" is detrimental to your marriage. I want my wife Ashley to have the confidence of knowing I'm not investing in ANY close friendship with a woman except, of course, for my friendship with her!

It all comes down to this...Your marriage will be stronger when your spouse is your best and ONLY close friend of the opposite sex. That might sound controversial, close-minded or even old-fashioned, but I'm firmly convinced it's the truth.

I'm certainly not trying to suggest that every person who disagrees with me on this point is destined for divorce, but please hear me out. I've seen far too many marriages end because of mistakes that were 100% preventable. I'm not saying you should never again speak to your opposite sex friends, but please at least consider the following points.

A close friendship with someone of the opposite sex is dangerous for a married person because...

1. Most affairs begin as a "friendship" that crosses a line

I've interacted with countless couples who had affairs and devastated their marriage and family as a result. Most of these people weren't on the "Ashley Madison" site actively looking to hookup with an affair partner. These people were surprised by the seemingly-harmless, subtle flirtation that ultimately led them to a place they never thought they would go. The bottom line is that when you put a heterosexual man in close, consistent proximity with a heterosexual woman, very often, feelings beyond friendship will emerge and if you don't have clear guardrails in place, those feelings could take the friendship down the dark path of infidelity.

2. You will often invest in this friendship at the expense of investing in your marriage

Time is the "currency of relationships," so to invest in any relationship, it requires investing your time. When we're investing ourselves into building and sustaining a friendship with the opposite sex, it often means we're taking time away from our spouse. It may also cause us to start looking for certain emotional needs to be met through this friendship that we don't feel are being met adequately at home, and even when an affair doesn't happen, this mindset can put a subconscious wedge between a husband and wife.

3. The friendship will usually cause feelings of jealousy and/or inadequacy for your spouse

In most cases where one spouse has a close opposite sex friend, at some point, the spouse who is not directly involved in this outside friendship will start to develop some feelings of inadequacy or jealousy. He/she will start asking questions like, "Why does my husband/wife seem so drawn to this person? Are they meeting a need I'm not meeting?" You must always take your spouse's feelings into account, and even if these feelings aren't vocalized by your spouse, they're still most likely present on some level.

Keep protecting your marriage and investing in your marriage

You might need to put some distance between yourself and a "friend" of the opposite sex, but it's small price to pay for a stronger friendship with your spouse!

This article was originally published on Patheos. It has been republished here with permission.