Derived from the name Narcissist which is drawn from a myth that dates back to 36 BC. Narcissus was a man well known for his good looks. He was so absorbed by his own features that he couldn't appreciate anyone/ anything else around him. As a result for his unique situation the gods cursed him. He fell in love with an image that he saw in a pond, what he didn't realize is that the image was a reflection of himself. He was so wrapped up in his image that he couldn't leave the pond. He eventually fell in the pond and drowned. When he died the pond wept, when questioned why, the pond said that he looked deep into my eyes but he never got to appreciate my true beauty.
Freud believed that narcissism is a necessary aspect of every human beings. It feeds and fuels the ego and provides a source of aspiration to live. Basically you love yourself so you will do any and everything necessary to preserve your life. I say it only becomes dangerous when you are in the extreme's of narcissism and you have lost an appetite for life outside of yourself.