Update: 5 months after cymbalta, I just want to let anyone who is suffering terrible withdrawal symptoms that many of my symptoms have diminished, and that memories and personality do return, sometimes spontaneously. I suspect that in another couple of months most of my symptoms will be completely gone, and I will be back to normal. Don't give up, the depersonalization, and derealization go away, slowly, but they do disappear, albeit slowly. Cognitive processes, memories, visualization, and creativity seem to come back spontaneously - I will find myself humming old songs, and thinking of memories that I was sure were totally erased from my brain.
It is not perminant, but it does last a long time, just endure.
Exercise 5-7 days a week, if possible, and use your brain alot, that is, do cognitively difficult tasks, in spite of the headache - this is critically important, and has resulted in massive improvements.
Again, this is not perminant, and these effects do go away with time. Do not give up hope, if I can do it anyone can.