Psychology Today explains:
Subclinical narcissists are happy. They are less likely to be depressed, sad or anxious, and rate their subjective well-being more highly. They're less reactive to stress, and recover more rapidly from it. Mild narcissism also seems to help people recover from accidents or other traumait gives them an unrealistic sense of their own invulnerability, and they believe that they will be able to handle whatever else life throws at them.
As one researcher put it, being somewhat narcissistic is like driving a huge SUV: You're having a great time, even while you hog the road, suck up extra resources and put other drivers at higher risk. A narcissist can be hard to identify, in part because he is likely to be much more fascinating than you would expect for someone so self-absorbed, and in part because you wouldn't think someone with such self-regard could be so defensive and needy.
Of course it also applies to people with really important hair as well.