" Narcissists have poorly regulated self-esteem, so they are chronically vulnerable. If they are vulnerable then there is the threat that they may get found out, so they often maintain a grandiose exterior. Because they always measure themselves by other people, they also measure themselves against other people. They are chronically reliant on the opinions of others to form their own sense of self and are always comparing themselves, their status, their possessions and their lives to other people to determine their sense of worth and self-esteem (in a way, narcissists outsource their sense of self). "

― Ramani Durvasula , Should I Stay or Should I Go?: Surviving a Relationship with a Narcissist