I agree that marriage is like communion--it's also a bond of attachment, and the capacity for a secure attachment first develops in infancy, but not always.  
There are spiritual aspects as well that aren't fully understood.  
 The wedding is the beginning but the relationship is a living thing that must be renewed. Sometimes the relationship dies and the hierarchy needs to recognize that.  But that death is a long process--it can be that the two spouses have grown emotionally in different directions, or that one has grown and the other has not; it can be due to a lack of communication skills where when differences arise and they fight, they don't know how to reconcile or other.  Each marriage is different just as each individual is different.  If Catholic priests were married they would have experienced this themselves and would understand it.  I know a number of couples who have been married for over 40 years, some up to 70 years.  How do they do it?  The Church should find out.