What does the song 'How to Save a Life' by Fray mean?

I'm not exactly sure but I always thought it was an account of losing a friend and lover. Sort of sounds like two people breaking up. Maybe the 'If I had stayed up with you all night, I would know how to save a life' refers to their last hope of rekindling their relationship and having what would have been their life together? I also really like this song, I remember when it came out a few years ago, but I agree it quite ambiguous. Hope that was useful :)