To begin with, it is almost always fornication hidden from family and friends, colleagues and so on. In most cases, this means that the novel comes to sex and drinking tea in the kitchen at the beloved: get together in a restaurant or theater - is dangerous to go on a weekend - is almost impossible to call a loved one evening and wish "good night" - even unthinkable .
In the presence of his wife and mistress, "the first violin" will always play a legal wife. And feel "second class" in this love triangle is extremely unpleasant - even fatal man (as often happens) proves that love to his wife for a long time has passed, that they share only the children that he soon will submit a divorce, that's just come up, how to tell his son ... This situation can drag on for years, and all these years unfaithful husband will feel guilty towards his wife. And if it is his weary - will take part irritation "treacherous temptress."
Relationship as a free and with a married man can arise in different ways. But in the case of any problems with the free man, you'll solve them together. And in the case of a married intervened "third party" - a legal wife in the person that you are virtually guaranteed to make enemies. And it is very difficult to predict what steps against you it can be done - even if you do not plan to destroy the family, and just wanted to have a good time.
And the main thing. If you're having an affair with someone else's husband - in most cases you are dealing with a callous man who does not care about feelings of others, or to the person impulsive, unable to be true, spitting on obligations to other people, besides a liar ( and who called his wife from the bed of his mistress, and assured that stands in a traffic jam?). Add to this the "bouquet" of neurosis and even in the long term (such is the fate of almost all men were "caught in the middle"). Tell me honestly - would you like to see next to each such "ideal"? And where you have a guarantee that by changing the wife with you, he does not ever change with someone you?