"But we're just friends" are four of the most dangerous words for your marriage.

But over and over in my office and on the phone I hear it: "We are just friends, there is nothing going on."

The majority of extramarital affairs begin as "just friends." While it is certainly true that there are affairs that begin with impulsive one-night stands with a stranger, the most common ones that I see begin as "just friends." In fact, if you find yourself thinking or saying "but we are just friends" you are probably already in trouble.

Gary Rosberg of America's Family Coaches states that there are at least 19 stages a person will pass through on the way to physically consummating an extramarital affair. There are at least two important notions that we can lift from Rosberg's statement:

1) At each and every one of the 19 steps, you have a clear choice between going further down or stopping the process. In other words, these things don't "just happen."

2) An affair - by the way, I hate that term!

It makes it sound like it is this wonderful experience with no consequences ... as in "It was a grand affair." In my marital counseling and relationship coaching experience, adultery breaks up marriages, wrecks families and crushes kids.

Anyway, now that my rant is over, an affair becomes adultery long before the physical act. In fact, emotional affairs can be stronger and more difficult to get out of than physical affairs.

The late Shirly Glass was a pioneer in the area of emotional affairs. In her 2003 book "NOT Just Friends: Protect your relationship from infidelity and heal the trauma of betrayal," Glass identifies three red flags that indicate that you have progressed from a safe friendship to a romantic emotional affair.

1) You feel closer to your friend than you do your spouse.

You find yourself thinking of this person more and more often and looking forward to the next time you are together. When something happens during the day, the first person you think of telling is this friend, not your spouse.

2) Keeping secrets.

You no longer feel comfortable telling your spouse about this person. You begin to cover up so as not to be found out.

3) An increasing sexual tension.

You admit your attraction for each other, but promise (complain) that you can never act on it. You fantasize what it would be like to be with this person. This helps to create a pretend world where everything would be wonderful if the two of you could just be together.

One of the most overlooked and dangerous facts about emotional affairs is that we are all vulnerable. If you believe that this fact does not apply to you, then you are even more vulnerable than everyone else.

How to protect yourself and your relationship

Keep clear boundaries. A boundary is simply what kids mean when they say "don't go there."

Avoid being alone with and/or emotionally close to someone to whom you are attracted.

Talk often about your spouse. "Spouse bashing" does not count. Talk about what you have done lately and what you are looking forward to with your spouse.

If you are going to talk about emotional issues in your marriage, make sure you are talking to your spouse, a trusted friend who is on the side of you and your marriage or a professional who is on the side of your marriage.

Be especially careful at work. More and more emotional affairs are occurring in the workplace. You spend time together, you go through crises together, you solve problems together. Do not make a habit of taking private lunches or breaks with the same person over and over.

Set up a review committee in your mind. Ask yourself, "Would my wife, my mom, my wife's mom, my sister approve of what I am doing right now?" or, "Would my husband, my dad, my husband's dad, my brother approve of what I am doing right now?"

If the answer is no, then I offer you what I call my RLH prescription.

RHL stands for Run Like Hell!

Here is a cold dose of reality: 75 percent of marriages between affair partners result in divorce.

In closing, remember that we are all vulnerable, watch for the warning signs, and protect yourself and your marriage.