Now that we’ve defined the circles, let’s add another layer to this analogy using traffic lights, where green light means “go” and refers to activities that bear no threat to your relationship with your partner, yellow light means “be cautious and be prepared to stop” and refers to activities that could potentially be problematic, and red light means “stop, do not go” and refers to activities you do with someone who is not your partner that are a clear breach of the promise of exclusivity that defines your relationship.

All activities in all three circles combined are green light activities if they are done with your spouse, whereas with someone who is not your exclusive significant other, only the activities in the outer circle are green light activities. Activities in the inmost circle are those that are exclusive to your relationship with your partner and thus are red light activities if you engage in them with someone else other than your partner. They represent breaches of trust and full boundary violations if done with someone else. Don’t go there. Full stop.

Activities in the middle circle, if engaged in with someone who is not your partner, are yellow light activities. Yellow light activities are those that are potentially open to a lot of different people in your life, not just your partner, but at the same time, they are activities that provide more opportunity and time to develop a connection and so must be approached with caution and awareness. Yellow light doesn’t mean that such activities are wrong. It doesn’t mean you shouldn’t do them. But you need to be cautious about them. Be open and communicate about them with your partner. Negotiate ahead of time about them. And if some of them make your partner feel uncomfortable, be prepared to stop them, and change course. If even just thinking about communicating about them with your partner makes you uncomfortable, that’s probably a good sign you should think twice about what you are doing.

I am sure that most married people or individuals in a committed relationship have met someone in their life, other than their partner, who, under different circumstances, in another life, with the right nourishment, could potentially have been a romantic partner. Perhaps you have been aware of people like that in your life since you entered your current, long-term committed relationship. For the purposes of this illustration, what would be examples of green light activities with such a person, assuming you are in a committed relationship right now? How are green light activities different from yellow light activities? What activities are clearly venturing into red light territory? Have you discussed these ideas with your partner, ensuring a shared understanding of what constitutes your sacred space? Open communication about these matters lays the foundation for a strong relationship.

The next thing I want to point out is how easy it is to lose your spouse’s trust. You might think that betrayal only occurs once you wander into the red-light zone, but that’s not the case. Breaches of trust in the red-light zone usually begin with breaches of trust in the yellow light zone. For example, lets look in on Sally and John, a committed couple. Sally just found out about some lunch meetings John had with an attractive female colleague at work, and she says to John, “Wait. You’ve been out to lunch three times with Freida from work? In the last two months? How come you never told me about that? And why did I have to find out that you were going out with her at all from Joan?” In this case, Sally already feels that a breach of trust has occurred and wonders why John was keeping this secret from her.

Very few people would ever feel the need to lie to their partner about green light activities, but they might feel the need to lie about yellow light activities. Why? Because on some level, they know their spouse might have a problem with it. Deep down the person drifting deeper into the yellow light zone senses they could be approaching forbidden waters. Consciously choosing not to say anything at all about it is to have a secret from their partner. That secret is a lie, a lie of omission, every bit as much a lie as a boldly stated falsehood. This is why I say it is so important that you communicate openly and negotiate with your partner about these types of activities. Transparent and continuous communication, even about potentially uncomfortable topics, is a key factor in building and maintaining trust.

Some yellow light activities are best avoided altogether, to avoid taking unnecessary risks, or to avoid the appearance of impropriety. Since the pain of crossing into the red-light zone and giving away your treasure—and your spouse’s treasure—to someone else is so great, it can be worth it to set up a wide “no go” perimeter so that you never get close to crossing the inner boundary. Such a wide “no go” perimeter might encompass a good portion of what falls in that yellow-light zone.

In other words, it may not be inherently wrong to go to lunch with someone you find sexually attractive, or to spend time with them in long daily commutes, etc., but it makes crossing the inner boundary more likely so it may not be wise to do some of these things, or at least don’t do them consistently with the same person. In this yellow area, activities with others need to be negotiated between you and your partner. You may both agree that there should not be hard and fast rules. There may be exceptions, but these exceptions need to be discussed and negotiated as they come up. And engaged in only once. Something you do repeatedly is no longer an exception, and it is the repetition of placing yourself in that yellow-light zone over and over that can lull you and desensitize you and wear away at your resolve and potentially draw you closer to the red-light zone with someone who is not your partner.