Take it from someone who knows this all too well, and has experienced it 10+ times: Taper, Taper, Taper. The three T's.
Withdrawl symptoms include irritability, moodswings, depression, flu-like symptoms, and in my experience, the worst of all, brain shocks.
Though these have been explained in a different thread, take my word, these make living nearly unbearable.
In my experience, whenever energy is exerted (ex. I stand up, I reach for a glass of water, I type...) an electrical 'shock' is sent through my brain, back to front and then back again. The most accurate description is that, though you may be standing perfectly still, it will feel as if your head just lurched forward while at the same time you were hit on the head with a baseball. It's fuckin intense. Check the health forum for a thread detailing all of this though.