They must have it all NOW, good or bad. By bringing the feared abandonment about, the narcissist can lie to himself persuasively. She didn't abandon me, it is I who abandoned her. I controlled the situation. But there is nothing, which reminds the narcissist more of the totality of his envious experiences than happiness.
Narcissists lash out at happy people out of their own deprivation.
Then there is narcissistic hurt. The narcissist regards himself as the center of the world and the lives of those surrounding him. He is the source of all emotions, responsible for all developments, positive and negative alike, the axis, the prime cause, the only cause, the mover, the shaker, the broker, the pillar, forever indispensable. It is therefore a bitter and sharp rebuke to this grandiose fantasy to see someone else happy. It confronts the narcissist with a reality outside the realm of his fantasies.