“When someone goes to the doctor and says, "I hear a voice in my head," he or she will most likely be sent to a psychiatrist. The fact is that, in a very similar way, virtually everyone hears a voice, or several voices, in their head all the time: the involuntary thought processes that you don't realize you have the power to stop. Continuous monologues or dialogues. You have probably come across "mad" people in the street incessantly talking or muttering to themselves. Well, that's not much different from what you and all other "normal" people do, except that you don't do it out loud. The voice comments, speculates, judges, compares, complains, likes, dislikes, and so on. The voice isn't necessarily relevant to the situation you find yourself in at the time; it may be reviving the recent or distant past or rehearsing or imagining possible future situations. Here it often imagines things going wrong and negative outcomes; this is called worry.”

The Power of Now (1997) p. 16