If they are friends you've known a while and have fun with, perhaps your reaction is a little extreme? If they don't know you are NPD, and since you are NPD, you've basically been putting on a big facade all this time to these people or friends of yours. NPDs are notorious for adopting a social facade that is false. So, really, who is false, except for yourself? Sorry to be so blunt, but isn't that the real truth of the matter? Maybe it's time to get more real with your friends, confide in them (the ones you may trust more) and let them know who you are and how you're now trying to change. Because perhaps you even made yourself out (in your false facade) to be the victim, when in fact you're most likely the perpetrator?

I wouldn't go to such extremes as discarding everyone you're close with --- I would gently and cautiously explore opening up more to maybe just a trusted 1-2 of these friends. And you may be very pleasantly surprised by the results if you do open up.