Editors note: Neil Rosenthal is out of town. This is from “The Best of Neil Rosenthal” series.

We know that for the past 30 or so years, the divorce rate has been stuck between 40 and 50 percent of marriages. We also know that some people who elect to stay together are not happy together. They remain with each other because of children, religious beliefs, economic necessity or fear they won’t do well on their own — but not because they are joyous about being together. Thinking about this subject has caused me to reflect on how hard it is for many people to sustain love, closeness and passion over time — no matter how much in love they are with each other when the relationship first begins.

Frequently, the process works like this: a series of minor unresolved grievances, small disappointments or petty grudges accumulate over time. Typically, these grievances aren’t effectively resolved. After a while, the person who is more hurt, annoyed or angry will withdraw from the other partner. This isn’t a giant withdrawal, and there may still be a lot of love and goodwill between the two parties. But sooner or later, the other partner will feel a greater coldness in the relationship, or less attentiveness and affection. So that person eventually pulls away or distances as well.

This is an ideal time for the two of them to talk about what has happened, to air their respective grievances, disappointments and hurts — and to repair the wounds between them. But most people don’t engage in this repair work, so the distance inevitably grows larger. Author Terrence Real (How Can I Get Through To You?) describes that the more he withdraws, the more critical and less loving she becomes. The colder and angrier she becomes, the more he withdraws. Let this go on for 20 years and what you have at the end looks like two decent people trapped inside a dying relationship. Says Real, “The degeneration of connection that spans years is made up of thousands of tiny incidents of disconnection that span mere moments.”

Before long, they are occupying themselves with separate activities and interests, because they feel less close and connected to each other. This is where one person might devote him/herself more and more to the kids, or to work or to sports. This is also where one or both are more vulnerable to meeting someone else and beginning an affair.

My point is that every relationship has this periodic minor repair work to do on an ongoing basis, so that small incidents do not mushroom into bigger issues. It is vital that the two of you are respectful, civil and constructive when talking about a conflict or hurt feelings — no exceptions. And you cannot respond with anger, aggression, threats or defensiveness if your partner tells you that s/he is hurt, angered or offended by something you said or did. Your partner has to tell you what’s bothering him or her — that’s how repair work occurs.

If you are part of a couple, make sure you do this ongoing repair work, by apologizing for wrong-doing, or words that hurt, or behaviors that offend, and specifically ask what your partner would prefer you say or do — or not say and not do.

This is the best insurance policy you can get that will essentially affair-proof your relationship, and it’s also the best opportunity you are likely to be given about how to live happily ever after with each other.

Neil Rosenthal is a licensed marriage and family therapist in Westminster and Boulder, Colorado. His column is in it’s 21st year of publication, and is syndicated around the world. You can reach him at (303)758-8777, or email him through his website: www.heartrelationships.com. He is not able to respond individually to queries.