I think similarly but different - break ups are often an error in judgment, the idea that something went wrong along the line. It might be there's a flaw with the system of monogamy (that's my conclusion and why I've had a very successful - thus far at least - non monogamous relationship for ten years or so. But if a relationship ends, there might've been an error in judgment, an error in process or a significant change.

I think the important thing is to behave a little like air crash investigators, work out why the error occurred without apportioning blame and to do that objectively as possible. Was it human error, systematic error, or an error caused by something outside the relationship?

Whatever the cause, the trick is to learn from it and take the lessons into your life and into the next relationship (if you want one). You can do this without pointing fingers and it means there is always something to learn at the end of every relationship, failure comes from an inability to learn and repeating the same mistake (staying in a dead relationship, or returning to the same sort of person) - failure isn't being single. :o)