Here it often imagines things going wrong and negative outcomes; this is called worry. Sometimes this soundtrack is accompanied by visual images or "mental movies." Even if the voice is relevant to the situation at hand, it will interpret it in terms of the past. This is because the voice belongs to your conditioned mind, which is the result of all your past history as well as of the collective cultural mind-set you inherited. So you see and judge the present through the eyes of the past and get a totally distorted view of it. It is not uncommon for the voice to be a person's own worst enemy. Many people live with a tormentor in their head that continuously attacks and punishes them and drains them of vital energy. It is the cause of untold misery and unhappiness, as well as of disease.

Eckhart Tolle

from The Power of Now: A Guide to Spiritual Enlightenment