In the movie Revolver (2005), the character Jake Green made a profound statement, “The greatest enemy will hide in the last place you would ever look”(—Julius Caesar 75 BC). [in a later conversation]…While playing, Avi says “you know what is so elegant about this little game, Jake? No-one knows where the enemy is. He’s inside of every one of their heads. And they trust him, because they think they are him. If you try to destroy him to save them, they’ll destroy you to save him.”
Often times, people fail to question their very own thinking / philosophy.
So, question your thinking. Your thought might be the enemy hindering your own progress. If the thinking is your enemy, kill the enemy before it kills you.