It's been exactly six months since the relationship ended. I asked my nearest, dearest friend today "How long is this going to continue? When will it stop hurting?" He didn't have an answer. I feel that I've handled my grief in the healthiest possible way-- the only possible way-- accept the relationship for what it was, then move on. At first, I'll admit, I was extremely confused, angry, hurt, maybe a little bitter. That's to be expected after any breakup, right? They say time heals all things. Eventually, you get over it, right?
Time helps, but it does not heal all things. For me, healing has been a long, exhausting process. I wish I could say I was there. I can say that I'm almost there.
I can't tell you how that process works, as it's different for everyone. I can tell you that it's absolutely necessary to have a support system. Your support will likely come from well-trained professionals (I was fortunate enough to find a therapist who was very knowledgeable on the subject), other survivors of pathological relationships and friends & family, though few people will genuinely understand the extent of your pain and anguish. Unfortunately, it's very likely that people won't believe you. The most valuable tool you can have is literature on the subject. Visit the library, search the Internet, read everything you can.
Grieving the loss of a Narcissist is very hard, there are many layers. Allow yourself to experience each stage of the grieving process...sometimes cycle through each stage several times, repeatedly.
Most Narcissists aren't diagnosed, because they either refuse to go to/continue therapy or because his charm and wit can fool even the keenest of psychologists (after all, he was able to fool you, right?). It's often the victims of narcissists who seek help. Fortunately, there is a wellspring of information available. Use it.