Chapters and Books

What is the right moment to walk away?  To not only end the chapter, but to close the entire book? 

My mom asked me for some advice today - which is not terribly unusual - and I did the best I could.  But it had a lot to do with the end of relationships and how to handle them.  I don't exactly have a very good track record with that myself.  It seems I have two modes of dealing with an ex.  Cutting all ties or having a rocky and uneasy friendship like thing.  I am not sure which is option is better - because there are pros and cons to each. 

I am sure those aren't the only two options in existance.  Just the only two I have ever used, with...questionable results.  And it just so happens that lately, that has been an area of reevaluation in my life.  Should I close those books?  Have I held back from doing so out of my own neurotic fear?  Or would I regret walking away later on?  I hate this sort of double guessing.  But these days I am much better at taking a few deep breaths and waiting to see a little longer.  Back a few years ago I would have thrown my hands up in frustration and gone with whatever was screaming at me the loudest at that moment in time.  Results were, again, questionable.

So when do you walk away?  When have you lost too much faith to keep going forward?  When is it time to look for a new path?