"When women make up their mind that the relationship is over, they stop talking about the relationship. Men interpret a woman's lack of complaining as satisfaction. But more often, it means she's given up".
(Dr. Lori Buckley, host of the relationship podcast, "On the Minds of Men")
In a 2004 AARP survey, over 25% of men who had been divorced in the previous year said that they "never saw it coming", compared to only 14% of recently-divorced women. "Sudden Divorce Syndrome" is a term used by counseling professionals and divorce lawyers to refer to situations in which one party---usually the husband---feels he was the victim of a divorce filing that "came out of nowhere".
Typically, such men become resentful and self-pitying, and will be eager to blame anyone but themselves for the failure of their marriage. "Everything was fine until those damn friends of hers started putting ideas in her head". "That greedy lawyer must have told her she'd be getting a big alimony award". "I'm sure there's some guy involved who turned her against me".
I mention in my book a friend whose wife moved out while he was away on a business trip, leaving a note taped to the refrigerator. He told everyone who would listen that she had given him no warning whatsoever, that she had always acted as if everything was fine. But when I ran into his wife a few months later she told me that she had, in one way or another, been trying to tell him of her frustrations every day for five years. At some point she just decided that she was sick and tired of talking to the wall. Enough was enough.
The big majority of divorce actions---as many as 75% in some states in recent years---are filed by women. I don't think that means that more women than men are unhappily married, but rather that women are more likely to do something about their unhappiness. Even unhappily married women, though, are not likely to act rashly. They don't normally pack up their clothes unless they've exhausted every other alternative. In fact, for years they may be knocking themselves out to prop up a one-sided relationship. But when a wife does decide to act, watch out. By then, she's already planning her post-divorce life, and there's usually no turning back.
The best advice I can give to men is to take their wife's complaints seriously. I'm not saying that wives are always right, or that some women---and men, too---like to complain just to hear themselves complain. But if a wife is complaining, it usually implies that she cares enough to complain, and that she hopes her complaints will lead to a resolution of the underlying problem and to a healthier marriage. If she's stopped complaining, and you haven't changed the behavior she was complaining about, you may be living in a fool's paradise, with a case of Sudden Divorce Syndrome soon to follow.