This is an excerpt of a lecture by the Siri Singh Sahib, Yogi Bhajan, as published on page 179 of the book, The Man Called the Siri Singh Sahib, published in 1979.
 
“The mind and the soul are polarities of Consciousness.  What makes them polarities?”  The void.  The soul looks at whatever is in your mind.  Your mind looks at whatever is in the void.  The soul is pure; it can’t do anything.  The mind is a combination of many different things.  It can’t stop; it is impossible to still the mind.  When you still the mind, it will tell you, ‘I am still, I am still.’  Don’t worry, I am still.’ And the moment it gets a chance it will run away. 
 
So, the best thing that you can do is to let the mind run away.  When the mind runs away, don’t move.  Instead, just say, ‘Ha, ha, ha ! Go, go, go.  I am here .  I am all right.’  Then out of shame, it will come back.  The mind can’t accept a challenge.” (March 18, 1976)