A child genetically predisposed to being psychopathic does not always turn out to be a psychopathic serial killer.
Children who grow up to be narcissists are either raised in emotionally invalidating environments where they were told to be perfect all of the time, or they did not get the love/attention/affection that they needed in the case of a sensitive and needy child.
They are too shy for the workforce, or they struggle to make adult friends.
They fight with their spouse and children in a negative way.
They do not receive unconditional or real love from their parents which celebrates them for exactly who they are and not who they pretend to be.
They are not allowed to make their own mistakes and learn from them.
Emotions are often there to give us important information.