The Consequences of Pathological Lying
Many people apparantly think that if you just believe your own lies, then they aren't lies!
Is this like that stupid question about a tree falling in a forest without anybody to see or hear it? In that case, some intellectual asks, "Did it fall?"
And if you believe your own lies, you're not innocent: you're just a double liar.
It takes little thought to see how a head full of lies is not a good thing. The brain is like a computer: garbage in, garbage out. Narcissists recklessly abuse their minds with garbage.
For one thing, a narcissist's need to think nasty lies about the good makes him unknowing of who his friends are and whom to trust. For another thing, his past could catch up with him at any moment, but he's got himself believing he's so special that he can get away with anything forever. So, he gets reckless, living as though his life is lived on a beach, instead of in a jungle where he has made many angry enemies. Also, he loses track of his various and changing versions of things, tripping himself up and confusing himself.
Moreover, you can't habitually force thinking to take tortuous, anti-logical pathways without damaging the brain's ability to think straight. I've known old narcissists. And I think that, as they age, the mind muddles.
Since much of his lying is through abuse of words, over time words melt together and lose their meaning to him. This becomes evident in his speech. For example, you might notice that his vocabulary becomes so limited he calls anything that comes in an envelope a "letter." No big deal? To the contrary, that's a very big deal, because words are what we think with!
He thus sabotages his mind so that, though he isn't senile and has no trace of Alheimer's, (a) he can't think his way out of a paper bag and (b) he cannot speak a five-word sentence without getting stuck at a loss for some common noun or verb that his brain can't come up with.
This is why narcissists really need to get real and stop abusing their minds. Peter Pan must leave Never Never Land and reach the Age of Reason. For his own sake.
Friends don't lie to friends. People who lie to themselves are their own worst enemies.