This is not the case. It runs against the grain. This is more of a BPD trait. A differential diagnosis of NPD actually almost rests on the absence of attempted suicide and self-mutilation. He finally refers himself to therapy, realizing that something is dangerously wrong with him.
Statistics show that all types of therapies are very ineffective when it comes to narcissists.
Soon enough, the therapist is bored, fed up or actively repelled by the grandiose fantasies and open contempt of the narcissist. He frantically gropes for alternative sources of narcissistic supply. Narcissists are very creative. The narcissist is bound to come up with a surprising angle. On the outside, he is likely to react aggressively.