Not to say that what you have is an addiction, but to fight my own addictions, I've had success with personifying the voice as someone separate from me, then I talk to it. When I think of it was a separate entity that's trying to inhabit my mind and steer my will, then I can decide what I'll allow it to do to me.

Sometimes it's too hard, but with practice I've found it helpful. I hope you can get some therapy, I think that would be really good.