FAQ #1:
Must two people remain in a marriage at all costs?

From Time for An Update On Marriage, Divorce, and Nullity, Archdiocese of Chicago:

Church law states that if either of the spouses causes "serious danger of spirit or body to the other spouse or the children, or otherwise renders common life too hard," the spouses may separate (c1153.1).  The Church is always concerned that human life must be protected from things that would destroy it.  If the marriage relationship is threatening the life or well being one of the parties or the children, or if the continuation of the relationship has truly become intolerable, then the Church reminds us of our responsibility to protect human life in all its form, and allows for the separation of the spouses.