I know in my own marriage I stayed in it to provide my son with what I thought was a stable background and to give him what I thought was the family life a child should have with two parents. But that isn't always the best way and it took me taking my son to therapy after the divorce to really see it.
The struggle for existence holds as much in the intellectual as in the physical world. A theory is a species of thinking and its right to exist is coextensive with its power of resisting extinction by its rivals.