Neti Neti - meaning "Not this not that" This meditation originates from the Vedas a 5,000 year old civilisation once residing in India.
Its main aim is to develop Clarity, Awareness and Realisation that which you are not. This meditation aims to release everything( identification) with all that you are not.
This helps particularly if you suffer from many negative thoughts, feelings which ultimately create suffering. If we choose not to identity with these thoughts and think that we are them we have the power to shift our Consciousness to a state of bliss.