Puzzling Thought

So the other day, I was describing someone's, ahem, rather unhealthy relationship to a friend of mine.  I concluded the story with 'she's usually very smart, she'd totally be able to see how wrong this is if it was happening to anyone else'.

Then I thought for a second.  I could pretty much say that to describe everyone I know who is in a questionable relationship.

Why is it that everyone can see problems with other people, but not with her own situation?  Are there some things in my life that I'm not seeing?  Are we all always bad at seeing things ourselves?  Do we actually listen to others when they point out problems to us?  I think I know the answer to this.  Can anything be done when we're in a bad situation?  Your thoughts?