There is a phrase the sociologist Catherine Hakim has coined for the kind of sexual affair that makes you happy but doesn't destroy your relationship, and that is "good infidelity".

One of our problems, she claims in her latest book, The New Rules Of Marriage: Internet Dating, Playfairs And Erotic Power, is that we don't practise enough of this, and indeed are all too disapproving of those love rats that do. This, she says, is one of the reasons why we have such high divorce rates both here and in America. We simply haven't cottoned on to the fact that a few fun and clandestine sexual flings – what she calls "playfairs" – are, for both women and men, all it takes to stop a long-term relationship withering of boredom or self-combusting. In other words, when you start to sniff that new scent on your partner's shirt, you should keep quiet and greet it as if it were the wrappings of a Viagra package found in the bottom of the drugs cabinet.

Hakim is not the only author to have a book out right now proposing the old rules are no longer relevant to these times and we are finding our way to a new code of relationship conduct – also published this month is Meg Barker's Rewriting The Rules – but hers is striking because it is telling us how we should live our lives. I don't mind commentators observing that we are too puritanical and that we need to be more relaxed about the sexual lives of others, including those nearest and dearest, but Hakim really does seem to be promoting the "playfair" and other secret dalliances as an antidote to our high divorce rates. "The fact that we eat most meals at home with spouses and partners does not preclude eating out in restaurants to sample different cuisines and ambiences, with friends or colleagues," she writes. "Anyone rejecting a fresh approach to marriage and adultery, with a new set of rules to go with it, fails to recognise the benefits of a revitalised sex life outside the home."

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If only it were so easy. And if only it were true that our high divorce rates were simply the result of our prudishness over the love rats amongs us. Hakim seems to neglect to mention that, while infidelity is one of the reasons given for divorce, it is not the prime one – which, in the UK, was recently found to be "growing apart". Meanwhile, one only has to look at the factors that drive break-ups (such as financial instability) and also the history of divorce (the explosion that occurred with the growth of feminism) to see that the picture is far more complex than a simple desire to escape from "the cage", as Hakim describes it, of fidelity.

She cites France as a nation that excels in good infidelity and the acceptance that in every long-term relationship must come the odd affair. In doing so, she fails to mention that the French have divorce rates only a little behind our own, and similarly high rates of cohabitation. In short, they are struggling as much as we are to make the endurance marathon of marriage work. Not only that, but while there are examples of lotharios like Dominique Strauss-Kahn, who appears to have been tolerated for his indiscretions, there are also the tales from France of husbands and wives who simply won't put up and shut up. Segolene Royal was one such figure, who pushed the father of her children, Francois Hollande, "to leave our home to continue pursuing his love interests".

Meanwhile, one could also look at Sweden, a nation tolerant of sexual infidelity, yet whose divorce rates are among the highest, and conclude her proposed link simply doesn't exist. Whether you pillory a man or woman who has an affair, or simply shrug your shoulders and say "c'est la vie", divorce and the break-up of relationships are part of the landscape of our lives.

At least Meg Barker's Rewriting The Rules is genuinely more interested in the real breadth of human relationships and lifestyle solutions that exist in the world today – whether they be open marriages, divorces that lead on to stable friendships or the parallel relationships of affairs. Rather than tell us how we should live, she is simply giving examples of how other people have already rewritten the rules. And this ultimately is what we have to acknowledge. There is no formula with which we can make the long-term relationship easy, no trick through which we can find the answer to living together for a lifetime. We have to let go of the idea that successful monogamy – if indeed that is what we want – is based around anything more than the chemistry of character, the chance factors of circumstance, and, yes, a certain amount of hard work.