The 38-year-old actress, who has two children with husband-of-eight-years Chris Martin, said that she knows people who have been unfaithful but that she tries not to think ill of them.
'I am a great romantic, but I also think you can be a romantic and a realist,' she told The Sun during a press conference at the Venice Film Festival for her new movie, Contagion.
'Life is complicated and long and I know people that I respect and admire and look up to who have had extra-marital affairs.
'It's like we're flawed. We're human beings and sometimes you make choices that other people are going to judge.
'That's their problem but I really think that the more I live my life the more I learn not to judge people for what they do. I think we're all trying our best but life is complicated.'
In her film Contagion, she plays an adulterous wife who accidentally brings back a deadly virus from Hong Kong to America, and joked that, '...If death by virus was a punishment for extra-marital affairs there would only be three dudes left in this world right now.'