Narsicissm can be managed if A) you are aware that you have tendency towards it, and B) you are aware that it's a BAD THING, a problem that you need to really deal with.
I have a history of diagnosed narcissist personality disorder in my family, and I have myself being showing... let's say traits of it too. I was also always very anxious about it (a bunch of lucky experiences have taught me, on a strictly rational basis, how invaluable healthy social interactions can be and how fucking them up is just not going to do me any good).
The irony is that I have heard quite a few times now how super kind and considerate person I am. I'm usually not bothering to explain it's just because I systematically check myself and basically force myself constantly to do the exact opposite of what my guts and instincts tell me to do.