When a man and woman become close friends, they enter into an unspoken pact — no sex. It ruins friendships.

Sarah and I were best friends until we broke that pact. For months, we had navigated the border of friend and lover, going on unofficial dates, touching each other like we were a honeymoon couple, and even sleeping in the same bed.

Despite our closeness, we never got to first base. We were just friends. Somehow, we managed to tiptoe around the point of no return until one night when we stampeded across it.

Neither of us called a timeout to ask the obvious — what does this mean?

The morning after “talk.”

The next morning, we hopped across the street for breakfast, holding hands as we stepped inside. The affection escalated when she wrapped her hand around my waist and gave it a squeeze.

It signaled what I had craved for months. Sarah was going to be my girlfriend. Only her stamp of approval remained, but I refrained from asking, hoping she would bring up the topic.

When the server slopped down our plates of pancakes, she dug in, and it became obvious I would have to make the first move.

“So,” I said. “What’s next?”

Sarah averted her eyes at first. Then, she mustered enough will to beam her inviting smile before opting for another cycle of bit, chew and swallow of pancake.

“You’ll probably hate me,” she said.

When did that opening salvo ever precede positive news?

She continued. “Can we go back to being best friends?”

Perhaps nerves had infected her judgment. Maybe she just needed time to reflect and think with clarity. These excuses sounded reasonable at the time, so I put off the discussion.

The picnic confrontation.

Two days passed. We met up in Central Park for a picnic we had planned before our tryst. I brought a bottle of wine and plastic cups for the liquid courage we’d both need.

Back and forth, we went about our future. I pressed her to give it a shot. We had practically been in a relationship before our night of passion, I explained. Nothing would really change.

Still, despite my emotional sales pitch, I could sense her indecision.

“Let’s go on a date, see how it goes,” I said. “It might surprise both of us.”

For some reason, she agreed.

To my surprise (and perhaps hers), we both enjoyed our date. Sarah got caught up in the moment and declared our status as a couple.

The honeymoon period

We lived the dream, but only for two weeks. Behind her smiles, affection, and bouts of lust, she hid an undeniable truth. Her heart lacked what her head wanted.

“I’m not sure why we’re together,” she kept saying when I asked what bothered her.

On our three week anniversary, she handed me my termination papers, suggesting a severance package before we departed — one last time for the road. I declined, thinking my refusal would preserve my dignity. Stupid me.

We made several efforts to reclaim some semblance of our earlier friendship, but that proved impossible. After a round of childish name-calling and accusations, we decided on a short cooling-off period until our emotions subsided. We hugged and said goodbye for the last time.

Male-female friendships can get complicated.

It’s not that sex always gets in the way when hetero men and women engage in a friendship.

It doesn’t. I’ve maintained several female friendships for over twenty years. I’ve also lost friendships because of unrequited love or, like in Sarah’s case, we gave it a go but failed.

That might sound depressing, but there’s an upside. It only needs to work once.

Two years after Sarah and I went our separate ways, I fell in love with another friend, a running buddy. That relationship turned into a marriage. See, it can work. Still, if you’re thinking of giving it a shot, learn from the lessons of my many failures and one success.

1. Don’t act on your emotions right away.

Feelings often pass. You might feel a tingle of desire early on, but as you become better friends, the infatuation wanes, and you realize that remaining friends suits you just fine.

Be patient and let time work its magic.

2. Pay attention to signals.

Does she hold her gaze an extra second before you say goodbye? Would he rather spend time with you than watch football with his male friends? Are you more affectionate than normal for two friends? Do these signals mount in numbers and escalate in intensity over time?

Intuition may not be full-proof, but it’s a solid indicator, especially when cues work against you. When they’re not into you, it’s hard to misread.

3. Decide if you’re willing to risk the friendship.

If you’re both so in love that you’re willing to risk the friendship to make it work, then take the chance. If one of you values the friendship too much to risk it, then question whether mutual desire really exists.

Consider this. Relationships have low success rates. Is it worth risking a friendship when your feelings don’t meet the threshold of Hell yes, let’s do this. I couldn’t live with myself if we never try.

4. Delay intimacy.

Before Sarah, I dated a friend from work. We were hanging out one night, both lonely, both tipsy, both aroused. We became convenient sexual partners who regretted our decision the minute it ended. Our friendship strained afterward and never recovered to what it had been.

Two consenting adults can do what they want, but sex can and often does ruin friendships, so consider waiting until you’re sure.

5. Cross the line carefully.

Do you come out and blurt your feelings, or do you allow things to progress organically?

In none of my friend-lover conversions did I announce my feelings out of the blue. Each one progressed organically to the point where we kissed first and talked second. There was no discussion, just increasing degrees of affection until we crossed the friend-lover line.

That doesn’t mean you can’t spew your feelings out of the blue, but it can create awkwardness when your friend doesn’t share the same feelings. As Sally said in When Harry Met Sally, “It’s already out there. You can’t take it back.”

Is it worth dating your friend?

One-hundred percent. Yes, it’ll likely fail, and you’ll lose a friend, but what if it works?

Lifetime friends are rare and even rarer when you harbor hidden feelings you cannot act on. If you both share a mutual desire, give it a shot. The odds may not run in your favor, but that’s always the case.