The Little Shaman is a spiritual coach & specialist in cluster B personality disorders, with a popular YouTube show and clients worldwide.
Narcissistic people have a different relationship with the truth than most people. For most narcissistic people, the truth is whatever they feel it is. For pathologically narcissistic persons, feelings are often understood as facts. They are considered truths, rather than just as feelings which are neither right or wrong. Because of this, the truth of the narcissist often changes with their mood. This is why they can seem so sincere about something and then an hour or a day or a week later, the situation is totally different. They may have meant it at the time, but when their feelings change, so does their perception. Things that seemed good are now perceived as bad, and vice versa.
This is often interpreted by people around the narcissist as lies and dishonesty, but in reality it's that their truth is not consistent. That's not to say that narcissistic people never tell blatant lies. They do, and it's pretty common. But they also have a very flexible relationship with the truth, even when they aren't intentionally lying. The truth changes frequently for them and often it seems to be whatever is most believable for them at the time, depending on how they feel. For example, when they are angry or upset, it is easier to believe bad or negative things - because these things validate their feelings, and their feelings validate these things. When they are not angry or upset, it is easier to believe good or positive things - again, because these things validate their feelings and their feelings validate these things.
This can be very hard for people who are not narcissistic to understand or deal with. For most people, the truth is not all that flexible. It is generally fact-based and does not change because someone's feelings do. For instance, most of us have reasons we don't trust someone. We can cite things they have done that have caused us not to trust them. Maybe they have been caught in a lie, or have been proven to have stolen something of ours. Because of this, we have determined based on facts that they are not someone we are choosing to trust. And that's usually how it stays. We don't trust this person implicitly one day but then suspect them of all manner of dastardly deeds and soulless motives because we suddenly feel insecure about ourselves the next day. This is illogical and unreasonable, but it is the way the pathologically narcissist's mind works.
It can be extremely frustrating to deal with someone who insists that their feelings are facts. "I feel your motive is bad and therefore it is!" is impossible to counter. It's illogical and as such, logic and reason don't work against it. People are confused by the accusations and upset that their character is being called into question this way - especially for no reason. This is also be doubly confusing when it's someone who just yesterday told you that you are the best thing that ever happened to them. One day they love their job. The next day it is the worst job they ever had. One day they hate peanut butter and always have. Next week they like peanut butter and don't know why you think they don't like it.
Dealing with the narcissist's version of the truth is not just frustrating, though. It leaves people unanchored, with no security and no safety. How can you believe anything that comes from someone whose truth changes with the weather? How can you build anything, do anything or plan anything with someone who could at any minute decide they never meant any of it and simply abandon everything - including you? How can you ever have any peace in a situation like that?
It's simple. You can't. You can't be a family with or a partner to someone who does not understand what truth and honesty really are, and whose feelings are so unregulated. It's further complicated by the fact that many narcissistic people also lie intentionally as well, sometimes continually. It can be maddening trying to figure out which is which or what is what. But the truth - the real truth - is that it doesn't really matter. It helps with understanding why this behavior happens, but in practical terms, regardless of whether it's an intentional lie or a temporary truth, you can't believe it either way. You can't trust it and you can't build on it. If someone cannot foster security and safety with honesty, there can be no trust. Without trust, there can be no relationship.