Legend: Once-upon-a-time nice guy hits middle age, has his annual PSA test, buys a red sports car, comes home and tells his wife that he's dumping her for a much younger woman.

Sometimes that happens.

But reality may more often go like this: Once-upon-a-time amenable wife hits middle age, has her annual mammogram, gets a promotion at work, comes home and tells her husband that she can't stand life with him any longer.

Modern marriage mythology is in flux. Divorce is seen mainly as a problem of young adulthood -- not a concern for grandparents. Surely after many decades together, couples have worked out the kinks in a relationship and are ready to settle down in their golden years. And many marriages do see a renaissance after the kids are grown and there's more time to spend together.

But the increase in health span after age 50 that opens the way to new careers and pursuits has also led to an increase in divorce among older couples, researchers report. At this stage, what holds couples together is the quality of the relationship; the lack of quality pushes them apart.

It also seems that women are more likely to initiate the breakup than men. According to a recent AARP study of more than 1,000 men and women who experienced a divorce in their 40s, 50s or 60s, 66 percent of women reported that they were the initiators of the breakup, compared with 41 percent of men. And husbands were more likely to be caught off guard by a marriage meltdown than wives. One in four men whose wives initiated the divorce didn't see the breakup coming. Only 14 percent of the wives were surprised when the husband walked.

"Perhaps women are more sensitive to issues in a marriage," explains AARP's Linda Fisher, who oversaw the research project. "They have more ability than in the past to do something about" a conflicted relationship. Women of a certain age today are more educated, more likely to be working, and have more financial security than their grandmothers might have had, she points out.

The top reason given for divorcing was emotional, verbal or physical abuse. Nearly half the women listed abuse among the three most significant reasons for breaking up a marriage, along with "cheating" and alcohol and drug use. Men also listed "falling out of love," which may be code for falling in love with someone else. This would be consistent with women's concern about infidelity.

At the same time, some form of abuse was a major cause for both men and women -- more important than sexual problems and issues with stepchildren or in-laws.

Sometimes marital abuse is long and brutal. A woman contacts me from the Florida panhandle. She doesn't want her full name used. She's starting over after 35 years of marriage to a man who gave her a few black eyes, threatened her with a gun. "He said he wanted to see my face explode," she says. He came after her with a screwdriver, a pair of scissors. She married at age 25. They adopted a son who is now in his 30s with a wife and baby daughter.

She finally left him when she was 61. The divorce was final a few months ago. "Despite my age and an uncertain future, I am happier and more content than I've been since I was a young woman," she says.

Most couples don't encounter this level of physical abuse, but many are nonetheless suffering in their marriages. As they look to the future -- their last hurrah -- they go through a period of re-evaluation, at work and at home. In some situations, is divorce the painful but necessary transition to a better life? As one man writes me in an e-mail: "How does one resolve the implementation of a 'My Time' lifestyle when the path seems to require the dissolution of a marriage?"

There is no one-size-fits-all answer. Marriages have a unique mystery that even spouses don't fully understand. What is significant here is that there is no age limit on asking the question.

Still, the experience of divorce is traumatic. Breaking up a marriage in midlife may also coincide with other losses in health and status. People in the AARP study generally felt that divorce was more emotionally devastating than losing a job, about the same as having a major illness and nearly as devastating as the death of a spouse. (Forty-five percent of the participants had lost a job, 30 percent had gone through a major illness and 8 percent had experienced the death of a spouse.)

People in the study ranged in age from 40 to 79; most were in their 50s and 60s. Nearly a third had been married for 20 years or longer. After the divorce, about 40 percent remarried or found another partner. The biggest fear for both men and women was being alone.

Yet, despite the turmoil, most gray divorcees -- 76 percent -- said they made the right decision in divorcing. More than half reported that they had a good quality of life; on a scale of 1 to 10, they scored themselves at 8 or above. They were optimistic. Looking ahead five years, three quarters saw themselves at 8 or above.

But happiness after a breakup doesn't mean that divorce itself is a good thing. It just shows how resilient people are in turning a crisis into opportunity.

A friend tells me about going to the 50th wedding anniversary of her in-laws. The adult children and their spouses and all the grandchildren gathered for the celebration. Champagne, toasts. The patriarch stood up and said for 50 years, it was all about family. And now, it would be 'my turn,' he said.

The next day, my friend and her husband got the news: D-I-V-O-R-C-E! The patrician parents were breaking up. The husband was leaving his wife. After the golden anniversary, the marriage was over. Everyone in the family was devastated. In time, the family healed. Each parent has written a new script -- good scripts, says my friend.

Even after a lifetime of marriage -- or anything else -- people now feel empowered to make significant changes. That's the hallmark of this new stage in life. For better or for worse.

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Are you in transition? Have you found your what-next? Are your primary relationships changing? Respond by e-mail to mytime@washpost.com. To send U.S. mail, see the address below; mark the envelope "My Time."