The voice in the head has a life of its own. Most people are at the mercy of that voice; they are possessed by thought, by the mind. And since the mind is conditioned by the past, you are then forced to reenact the past again and again.
The Eastern term for this is karma. When you are identified with that voice, you don’t know this, of course. If you knew it, you would no longer be possessed because you are only truly possessed when you mistake the possessing entity for who you are, that is to say, when you become it.