I would have to agree with the older women... that a marriage is a partnership... it is such a long commitment between two people that both involved will grow and change over the years... sometimes for the better... sometimes they grow apart. It's up to the determination of both to stay in it for the long haul... and when one gives up or strays... the other partner has to decide to carry on single-handed or let it dissolve.
Each problem is different and unique to that relationship. In some relationships... when a partner cheats... there might be enough honesty and communication in the relationship to allow for a reconciliation. Sometimes a partner decides to carry on in the relationship because they decide there are other things of greater importance than their broken heart --- it's their prerogative to make this decision and an understanding of this by outsiders is not a requirement. Other times, a partner may decide to dissolve the relationship because of the infidelity and this may be planned out... or... more often than not... it isn't planned out and emotionally driven.
There doesn't seem to be a 'one size fits all' approach to dealing with infidelity. The mentality of both partners involved influences the decision they make... and what they value most when the infidelity is revealed.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen