"It fails [marriage] for a complex set of reasons, most of which we will deal with later, but the major reason is that the protagonists get very scared that they are each going to lose their identities in the dependency, in the same way they lost them in the families in which they grew up.  The marriage begins to feel like a trap, a replication of the old family of origin.  So the couple begins to back away from each other, mistrusting."

The Family Crucible:  The Intense Experience of Family Therapy
Augustus Y. Napier with Carl Whitaker