FREE, ILLUMINED SOUL

The word yoga means "union," as in union with God, and while in English translations they are typically called aphorisms, a more descriptive term is the Sanskrit "sutras."  Sutra literally meaning "thread."  The first four yoga sutras read: 

This is the beginning instruction in yoga. 
Yoga is the control of thought waves in the mind.
A person who controls his thought waves abides in his real nature.
At other times, he remains identified with the thought waves.

Remaining identified with the thought waves means remaining identified with the "personality," or egoic self.  In his book How to know God: The Yoga Aphorisms of Patanjali, Swami Prabhavananda states that when the lake of the mind becomes clear and still, a person knows himself as he really is, always was and always will be.  He knows that he is the Atman.  His "personality," his mistaken belief in himself as a separate, unique individual, disappears.  The "personality" is only an outer covering, like a coat or a mask, which he can assume or lay aside as he chooses.  He who sees this is known as a free, illumined soul.