A bad marriage must break.By bad I mean abusive relationship, no warmth between partners, cheating, marriage due to societal or parental pressure etc.
And many a time children are adversely affected by the problems between parents. In such cases the two should separate, so that the kids don't have to see the ugly fights.
And the children would face a difficult a time initially, but if they are made to understand that their parents are individuals too and their happiness lie not in togetherness but separation, they will try to come to terms with it.
But just for the sake of children if one continues with a family that is unhappy, then it is hypocrisy. There is no harm in breaking a family where one is not happy although our traditions tell us otherwise. Perhaps it's time to set new orders and bring in new traditions.