A relationship like that is bound to become very emotional - and therein lies the trap. Because everything is fine as long as you do not show any emotions except deep sympathy and sweet understanding. But go and use one wrong word, make one comment that is not one hundred per cent affirmative, and you will raise hell. Neither a wholehearted apology nor a thousand good deeds will make up for one little, inconsiderate mistake.
All the affection they might have felt before turns into disdain. Suddenly they dispise what they were about to love, and every attempt to talk it over and calm down some of the emotion involved in order to keep the whole thing in perspective is rejected with an attitude so cool it might freeze your soul. I never really got that, because I stronlgy believe that a single bad moment is not worth letting pass by what might have been a great chance for both parties.
The only explanation I can think of is that the moment you show the slightest sign of a critical perception they feel deceived and lose their faith and immediately start to feel embarrassed about all the weak spots they revealed to you and the secrets they let you in on. So, in a belated (and as much irrational as incomprehensable) attempt to arm and to protect themselves by hindsight, they start acting cool, like nothing you learned about their delicate, vulnerable souls had ever been true... and they love to leave you with the impression that you were the worst thing that ever happened to them.
Well, poor things. Being in pain, or suffering from some bad experiences in the past does not humiliate anyone. It is absolutely natural, and after all it is what makes us human. And lovable. Nobody has to be ashamed of their wounds and weaknesses... But denyal will not ease the pain, and to push away people who have seen "too much" of one's soul will not make you stronger. The answer is talking it over, and I am good and ready to do so.