Thought-Power

Thought is not essential to existence nor its cause, but it is an instrument for becoming; I become what I see in myself. All that thought suggests to me, I can do; all that thought reveals in me, I can become. This should be man's unshakable faith in himself , because God dwells in him. -Sri Aurobindo 

One must not admit bad thoughts into oneself under the pretext that they are merely thoughts