Q. I have been married to my second husband for 20 years — and I’d rather be alone.

My husband isn’t a bad man. He hasn’t had an affair, he doesn’t do drugs, he isn’t physically abusive and he is also a loving father to our 18-year-old daughter and to my 26-year-old son from my first marriage. However, he is inattentive and uncommunicative with me, and we still can’t agree on the big issues: money, sex and parenting. There has been only a little improvement even though we’ve been in counseling for years.

The past five years have been particularly tough. We lost our jobs. We started freelance careers. And I’ve had to deal with my mother’s inoperable cancer as well as my own health problems. These crises have taught me that I cannot depend on my husband.

I stayed in the marriage years longer than I wanted, because I didn’t want my daughter to go through a divorce. Now that she is a college freshman, however, I’m wondering how much longer I have to wait.

When is the best time to tell my children that we are separating?

(Hadley Hooper/For The Washington Post)

A. In a perfect world, the time to tell the children is never.

This is not a perfect world, however, and neither are the people in it. If you and your husband have deeply different temperaments — and it sounds like you do — you know that these differences can stress a marriage and even kill it.

Even without those differences, you would probably run into problems, because marriage, like life, is a journey. There are often stretches of time, particularly in the early years, when it is intense or exciting. When the children are in their middle years, it can be tedious, exhausting and just plain boring. And then peace arrives and with it the ability to ignore each other’s eccentricities or to find them rather endearing.

But crises come tripping along, and, as you have learned, they can topple weak relationships so easily.

Before you take the long hike, however, you really ought to ask yourself whether there is anything you can do differently, because it’s a lot easier to change yourself than it is to change someone else. Even if you change only 5 percent — which is probably the most you can do — your husband will change just as much.

You might also search online for a “premarriage questions list” so you and your husband can take the quiz to see whether you are as incompatible as you think you are. You may be surprised to discover that underneath it all, you still share many of the same values and the same interests.

If that’s the case, you’ll slog through the reconciliation process better if you read “A Short Guide to a Happy Marriage” by Sharon Gilchrest O’Neill (Cider Mill Press, 2009) and “Why Can’t You Read My Mind?” by Jeffrey Bernstein and Susan Magee (Da Capo Press, 2003). They should give you some much-needed support and may even teach you to ignore what you can and to forgive what you can’t.

You might also look for a counselor who uses a different approach. Some therapists suggest that their clients write about their feelings, for instance, rather than say what they think, because it would give them a little more time to reflect and to express themselves more clearly and more kindly. The results could be a revelation to you, especially if you find out that your husband expresses himself better on paper than in speech. Some people like to communicate verbally — and some don’t.

If, however, this test simply proves that you and your husband have little in common and that divorce is your best option, then you can use it to explain the situation to your children, when you tell them that you may separate. But don’t stop there. You also need to ask them when they think this separation should take place and when it would hurt them the least.

Separation and divorce can be — and usually are — quite hard on children, even at 18 and 26, but it won’t be so bad if you let them down gently; ask them to help you decide on the timing of the separation and continue to be friends with your husband because, in a sense, you will always be married to him. You will meet at emergency rooms and maternity wards, weddings and funerals or wherever your son or daughter needs you. Such is the power of children, whatever their age.

Questions? Send them to advice@margueritekelly.com.