Separating Feelings From The External World (Narcissists Often Can't)

The thing about people who have various forms of Narcissism is that no one close to them is tolerated to have any kind of emotions that don't make the N. person feel good, happy, cared for, safe, praised, or powerful. This is where a lot of the "eggshell walking" comes from.

("BPD". PTSD and other boundary issues can share this problem, but not for exactly the same reasons; the person with Narcissism will reject, discard, and turn on others for this, while BPD and PTSD usually simply feel affected or controlled and may become upset, even defensive, but won't viciously discard the person or "retaliate".)

Normal communicative exchange is literally not possible, because you might insert some kind of emotional expression into your speech that cause them serious discomfort, or triggers them to feel defensive, or to retreat, withdraw, rage, or discard you. Or you might express that you like someone or something that the N. is envious, jealous, or afraid of, or you might express positive energy, optimism, excitement, or joy about something or someone.

Their own emotions, feelings, are what they're reacting to, just like every other human being. The difference is that people with Narcissism issues think that all of their feelings are representative of actual reality. They don't identify what they FEEL as their own internal reactions and perceptions; they think that the external world was the SOURCE of their feelings.

So if they felt fear when they looked at the spider, the spider to them is CAUSING them to be afraid, it's the SPIDER, not their own brain function.

If they find another person physically attractive, it's the PERSON DOING IT, they are MAKING themselves "be" attractive, they are CAUSING the feelings, like you would "cause" a cart to move by pushing it.

They are very likely to assume that EVERYONE finds the person attractive in exactly the same way as they do, because they don't know that it's THEIR OWN brain that's causing their feelings.

So if YOU make some kind of noise that sounds like frustration or annoyance, and they feel a twinge of something when they hear your noise, they won't see each thing as a separate thing (your noise, what your real reason for the noise was, your feelings being just as valid as theirs, and their assumptions about your noise and your feelings, and their emotional reaction to the noise.)
You made the noise therefore you CAUSED THEM to FEEL the twinge (of whatever feeling they had in reaction to it). Therefore you're DOING IT TO THEM, and BEING "CONTROLLING" or "PASSIVE AGGRESSIVE" TOWARD THEM.
People who interpret everything another person says, does, and expresses as having a hidden agenda or covert meaning likely have some form of paranoia, and may be projecting someone else's behaviors from their past onto a new person. Obviously not getting treatment for this will probably destroy a relationship.

They may also be revealing that THEY have hidden agendas and meanings behind everything THEY do and say, and they're projecting their behaviors and motives onto the other person.