"... Why is a person with NPD so easily hurt, yet can not comprehend how their own words and actions hurt others? And if they become self-aware of this (temporarily), what happens? Thank you again, you are very brave and have provided invaluable insight."
Here is my attempt to answer:
From my experience, what basically happens is the Narcissist reacts more to YOUR raw emotions when she or he are getting "hurt"(perhaps the absence of their own emotional phone is to blame for this extra sensitivity, sometimes also combined with being hyper-alert after having to rely on that trait to survive abusive childhood)- so they just "catch" what you feel and start feeling it and then experience this violent reaction of having to "push" it out and resist feeling unwanted emotions that they perceive as a weakness, and then also the emotions that come as a reaction to those, like shame, guilt and so that manifests outwardly as rage at you for "making" them experience those emotions.
Suppose you came to them wanting more intimacy, some empathy or when you were saddened or upset by something. Internally, they view vulnerability and emotional openness as a weakness and then also a threat. Often having survived abuse in their childhood they mistakenly attribute the predicament to themselves being too "trusting", vulnerable open and so on and so they fear and so try to avoid experiencing those emotions to avoid re-experiencing the trauma (which they often consciously "forgot") or even having to witness and therefore being reminded of those emotions and therefore of that perceived weakness.* It seems they can not react in a healthy way to your hurt or reaching out for empathy - to them it is just an attempt to shame them, to show them how they are to at fault. Once they catch those emotions and perceived implications of those, they will, of course, will try and avoid feeling the pain by turning around and "defending" against you, blaming you and making it all about themselves.
Suppose you came to them wanting more intimacy, some empathy or when you were saddened or upset by something. Internally, they view vulnerability and emotional openness as a weakness and then also a threat. Often having survived abuse in their childhood they mistakenly attribute the predicament to themselves being too "trusting", vulnerable open and so on and so they fear and so try to avoid experiencing those emotions to avoid re-experiencing the trauma (which they often consciously "forgot") or even having to witness and therefore being reminded of those emotions and therefore of that perceived weakness.* It seems they can not react in a healthy way to your hurt or reaching out for empathy - to them it is just an attempt to shame them, to show them how they are to at fault. Once they catch those emotions and perceived implications of those, they will, of course, will try and avoid feeling the pain by turning around and "defending" against you, blaming you and making it all about themselves.
(I can only imagine how puzzling and discouraging it is to be treated like this when you came to a person for empathy or understanding... :/ )
Now, In case when the Narcissist is the one who is hurting someone, they do not really feel anything inside (I know, kind of a horrible thing to say - but do see my point, it is not quite the "usual" implication) - in a sense that they do not really "set out" to hurt you the way they inevitably think you are doing when they are getting "hurt". They do it by NOT caring, by NOT showing emotions, by making sure you are not able to experience them in that way. In their mind they are almost giving you a favor by being so "shut down" and removed, because to them if they do not "bring" their emotions to the table then you can not be affected, since their only mechanism of experiencing discomfort is by "catching" your emotions. In a way it's like they are lacking initiative in the most basic way - they write themselves off as a person who can experience true emotions and therefore also as a person who can AFFECT other's true emotions. You see what I mean? (I don't blame you if you don't at first, I bet it is a puzzle for any regular person to think that way) They have not been really 'hear" or "seen" as an actual person when they were forming as persons, so they got used to the idea that their actions and feelings DO NOT truly matter. And in the rare event that they become for a second aware of those buried (and by now totally destructive feelings, they think the dutiful thing to do is to "shove it down" as deep as possible and pretend they do not exist. So if they do not "impose" their feelings on you which, they figure, should make you happy and they are genuinely puzzled when you feel dissatisfied with that.
Narcissism is like a delicate dance of constantly having to re-balance internally, and get the best hold you can of all those explosive feelings and blaming, harsh, criticizing voices in you, while out worldly trying to present a composed, impenetrable nearly perfect "front". It is exhausting, thoroughly dissatisfying and incredibly persistent - one can not simply stop and catch themselves for any length of time - once they are aware their frightened tiny inner being pushes them back into the "game' since there is not enough psychic energy to confront whatever the person fears feeling through.
As for being temporary aware, I can only speak from my experience and that "realization" always catches me speechless, and I become quiet and kind of (very mutely sad, because I honestly have not an earthly clue how to stop behaving that way towards the very same people who care about me most. Just a rational realization in my mind, while better than nothing, does not amount to much - to re-condition one's behavior, or in this case, their whole personality - their entire perception of the world and of themselves - that takes much more than a moment of intellectual awareness.
I attribute the limited progress that I made to the dogged determination to "dig deep"and figure out what had happened to me as a child and why am I experiencing this combined with the willingness to get through as much emotional pain as needed in order to see the truth, the reality of what IS my familiar situation and my make-up as a human being. It is the almost scientific curiosity coupled with the love of discovering the true "motive" behind things that lead me there initially, not necessarily the effect I was having on other people (pardon), though it did play a role later if only by intellectually realizing my responsibility towards others, without the "stick" of corresponding emotions to really make it, well, felt...
Please don't forget that all people are different, and Narcissism IS, after all, a spectrum disorder (even if this was said so many times it lost its original meaning lol)) I hope this helps to a degree, though I feel a little bad that I did not have more encouraging view. Thank you again for your initial question and please do feel free to ask again, comment and share what you think.
Best wishes to you!