So when you listen to a thought, you are aware not only of the thought but also of yourself as the witness of the thought. A new dimension of consciousness has come in. As you listen to the thought, you feel a conscious presence—your deeper self—behind or underneath the thought, as it were. The thought then loses its power over you and quickly subsides, because you are no longer energizing the mind through identification with it. This is the beginning of the end of involuntary and compulsive thinking.

Eckhart Tolle

from The Power of Now: A Guide to Spiritual Enlightenment