As we begin to develop awareness of the mind, the mind itself appears to divide into two. A new aspect of the mind arises. This is referred to variously as the witness, the seer, the knower, or the observer. It witnesses without judgment and without comment. Along with the arrival of the witness, a space appears within the mind. This enables us to see thoughts and emotions as mere thoughts and emotions, rather than as ‘me’ and ‘mine.’ When the thoughts and emotions are no longer seen as ‘me’ or ‘mine’, we begin to have choices. Certain thoughts and emotions are helpful, so we encourage them. Others are not so helpful, so we just let them go. All the thoughts and emotions are recognized and accepted. Nothing is suppressed. But now we have a choice about how to react. We can give energy to the ones, which are useful and skillful and withdraw energy from those which are not.
from the book “Reflections On A Mountain Lake: Teachings On Practical Buddhism”