Even water can kill you if you drink too much of it, and at some point, the normal narcissism continuum that most of if not all humans are on gets to be too much of a good thing, and you are going into pathological narcissism. Usually this is heading towards Narcissistic Personality Disorder or something close to that.
Pathological narcissists are not acceptable. They are not ok. They are not all right. They don’t live longer than others. They’re not happier or healthier than others.
Instead of being ok, the truth is that they are simply ill. It’s not normal for a human being to be that way, as it clashes badly with smooth social and occupational functions. It’s a maladaptive disorder because it turns you into the biggest asshole on the planet, and understandably causes a lot of people to dislike you just about everywhere you go.
People with NPD are generally quite damaging. They tend to damage or harm most of the people they are in relationships with. Why? Because that’s just what they do. They can’t really do anything else. Of course they have no insight, and most are utterly incurable. The longer it goes on, the worse they get, and by the time they are in their 40’s or 50’s, almost all of them are completely hopeless and often profoundly ill cases.
As you might expect, therapy with NPD’s is typically a monumental waste of time and often quite unpleasant for the therapist to boot.