Try to learn how to identify and avoid people with NPD. Do not let them into your life. I have a relative that was married to one until we found Dr. Sam Vaknin's info. NPDs are impossible to deal with. They refuse help because they believe there is nothing wrong with them.
http://samvak.tripod.com/9.html
Pathological narcissism is a spectrum of disorders. People suffering from the full blown, all-pervasive, personality distorting mental health disorder known as the Narcissistic Personality Disorder (NPD) - are, indeed, more prone to violence than others.
Actually, the differential diagnosis (=the difference) between NPD and AsPD (Antisocial PD, psychopaths) is very blurred. Most psychopaths have narcissistic traits and many a narcissist are also sadists. Both types are devoid of empathy, are remorseless, ruthless, and relentless in their pursuit of their goals (the narcissist's goal is narcissistic supply or the avoidance of narcissistic injury).
Narcissists live in a state of constant rage, repressed aggression, envy and hatred. They firmly believe that everyone is like them. As a result, they are paranoid, suspicious, scared and erratic.
Any person - known to the narcissist or not - who is perceived by the narcissist to be a source of frustration is in danger of becoming the victim of violence. If you disagree with the narcissist, criticize him, or deny him the unfettered and instantaneous fulfillment of his wishes - you become his enemy and the target of his unwelcome attentions.
Narcissists are fully aware of the difference between right and wrong and are fully capable of controlling their impulses. They simply do not care enough about their victims to do so. They lack empathy, are exploitative, feel entitled and superior and thus regard other people as objects or as extensions of themselves.
In his mind, the narcissist is superior in every way. This fantasized and grandiose superiority is what maintains the precarious equilibrium of his personality.
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Sounds like most traders!