How to treat the love affair offered by the third one like that in the film Painted Skin?

Hello， morning

It is a quite difficult topic, since it happens frequently in this modern society. No one can say they can absolutely avoid this situation.As modern society brings us with human right, it at the same time takes the human right of some other people. Modern people become more and more self-oriented and think less for people around them.
Since a third one in love relationship and marriage becomes more common, some people think it rational to accept a third one and attribute the mistake to the third one. They will say that the third one offers first. It is quite ridiculous. But we can not say that in this world there is no kind people, there is, they are who can resist the third one and insist in the family and his wife(her husband). In whatever society, morality is eternal good quality. Bad marality is not against the law, but the conscience will be scolded.