One has to mentally reduce all the three states as mind by perfect understanding of "what is what".

Adopting the neutral, impersonal point of view of the Witness also helps us transcend form, time and space. In fact, the memory of the past, knowledge of the present, and projection into the future require the existence of a consciousness which is in itself outside form, time and space. By learning to view and judge the three states on Witness position can transcend a sense of form, time and space, which helps to reduce its grip of duality. 

One has to mentally reduce  all the three states as mind by perfect understanding  of "what is what". The first effect of this practice is a lessening of the impact of individual experience. In the next stage, one has to train himself to ask where the mind dwell. The answer one arrives at is: in the Self, the consciousness! The three states come and go; what remains after they vanish is the consciousness which contains them. It alone is real. 

Meditation remains necessary only in preliminary stages, but meditation is not the means to acquire Self-Knowledge. The highest state attainable by yoga is no better than deep sleep. Only the path of reason can by itself lead to the realization of ultimate truth. –FORMLESS PATH