In high school I had a crush on Katie Brown (not her real name). She also had a crush on me. Neither she nor I knew it until more than 15 years later. By that point, she was divorced. The thought of striking up a romance at this late date never entered my mind. I was happily married with children and completely intent on avoiding an extramarital affair.

Katie had recently moved to Portland, Oregon, from out of state. My wife and I ran into her at church, and began inviting her to hang out with us. One evening, we invited her to go out with our family. She brought her daughter. We went to Oaks Park, a small amusement park along the Willamette River on the south side of Portland. Katie wanted to ride on The Spider -- a ride that spins people around at high speed as they rise up and down in pods. Each pod had room for two people.

WHAT MARRIED COUPLES BADLY NEED FROM YOU

Katie's daughter wasn't tall enough. My wife didn't want to go, but encouraged me to go with Katie.

Before I could answer, Katie put her hand on my arm. "Yes, let's do it!" she said.

Her touch might have been innocent, but it scared me. My high school crush was gone, but I still thought she was as attractive as she was then. I felt myself getting too close to a boundary I'd set to protect my marriage.

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I glanced at my watch. "I think it's time for us to go," I said.

Many people believe it's possible to prevent an affair by having a marriage bound together with mutual love and dedication. My marriage met both criteria. But the late Dr. Shirley Glass called this the "Prevention Myth." The claim that a happy marriage will prevent an affair has no evidence to support it.

Dr. Glass was a psychologist, a researcher and a therapist, and one of the leading experts in marital infidelity until she died in 2003. Through her research, she concluded that the true prevention of an affair relies on taking the following precautions. These are included in her book "Not 'Just Friends': Rebuilding Trust and Recovering Your Sanity After Infidelity."

1.) Recognize that attraction is normal.

My wife and I were having problems early in our marriage. We went to a professional counselor for help. One day, while meeting alone with our counselor, I confessed to him that I'd been feeling an attraction toward other women.

I worried that my feelings of attraction toward other women meant I was losing interest in my wife. The counselor assured me this attraction I was feeling was normal. I haven't worried about it since.

If you're attracted to someone else, it doesn't mean you're married to the wrong person. Feeling attraction isn't the same as feeling lust. Deciding to remain faithful to your spouse and taking actions to avoid being lured away by another person is the test of true commitment.

2.) Don't fantasize about cheating.

Men and women who've had an affair often admit they first crossed the line of infidelity when they imagined themselves alone with a person they felt attracted to. These fantasies created excitement and a craving for a real relationship. Fantasizing about the other person made it easier to take the next step of creating an opportunity to be alone.

3.) Don't flirt.

Flirting often begins by making frequent eye contact with accompanied by a smile. Next, we find excuses to talk to the other person. Then comes subtle touching on an arm, shoulder or hands.

Flirting sends a message that you're available. Save flirting for your spouse.

4.) Avoid risky situations.

Half of the women and 62 percent of the men Glass counseled in her clinic started their affairs at work. Work situations put men and women in close proximity to each other in ways that can create risky situations. If we become complacent, we can succumb to those risks, and cause severe damage to a marriage.

Know your boundaries. If working with a co-worker is causing you to make excuses to be with that person, you're in danger.

Also, be careful to avoid emotional affairs. It's becoming more common for men and women to identify a co-worker as a "work spouse." A work spouse is a co-worker with whom a person shares a special relationship, with bonds similar to marriage -- but without sex. The relationship is supposed to be platonic.

Work-spouse relationships can develop into emotional affairs that can be just as damaging to a marriage as a sexual affair. Telling your spouse about this kind of relationship is likely to arouse jealousy -- and for good reason. It's emotional cheating.

When working with persons of the opposite sex, it's important to be vigilant about the risks that exist. If you wish to keep your job, some risky situations may be unavoidable.

When work assignments require you to work alone with a person of the opposite sex, talk about it with your spouse. If you feel like you need to keep secrets about your relationships with co-workers, that's a sign that something's wrong.

Keep in mind that drinking alcohol will impair your judgment. It's wise to avoid drinking in situations that pair you up with a co-worker to whom you feel an attraction. If your work requires you to travel together, don't go near each other's hotel rooms, of course -- and make a habit of having a phone call scheduled with your spouse after work.

Jon Beaty, a life coach and father of two, lives near Portland, Oregon. He's the author of the book "If You're Not Growing, You're Dying: 7 Habits for Thriving in Your Faith, Relationships and Work."