I agree with wolfsong. The conundrum with these people is that to "successfully" navigate a relationship with them in regard to your own personal mental health, you must set strong boundaries and make a firm stand against their behavior. This is a constant struggle that few can continue for very long because they will never learn from this and accept your boundaries. The NPD will only be amicable when, in their mind, they have won or are "one up" as they say. They can often achieve this by simply ignoring you (silent treatment) until you acquiesce and come crawling back begging for some morsel of humanity. There is no ability to compromise or even "agree to disagree" in them. If they view you as someone who will provide them approval (supply) and reflect their false self, they will tolerate you (your are forever "on trial"). But they are always hypervigilant against injury and will summarily discard you when you are no longer a source of this supply. In fact, they know (subconsciously or not) "you are on to them" and their reaction is simply a defense mechanism against this threat (shaming) to the false self which could expose their self imposed, "flawed" true self. Once you are no longer useful to them you are persona non grata. As difficult as it is, consider yourself blessed to be free from their sphere of control.