There is no bigger mistake than the idea of "I." It is the biggest obstacle on the path to truth. Those who don't overcome this obstacle will never make any progress on the path of truth.

A sannyasin was passing through a village. A sannyasin friend of his was in the same village, so he thought he would visit him before moving on. Although it was nearly midnight, he went to meet him. Seeing a light shining, he knocked on the window. A voice came from inside, "Who is it?" Thinking that his voice would be enough to identify him, he simply replied, "It is I." But no answer came from inside. He knocked on the window many times, but there was no reply. He began to wonder if the house was empty. He said loudly, "Friend, why aren't you opening the door for me. Why don't you reply?" A voice was heard from inside: "Who is this fool who is calling himself I? Except for God, nobody has the right to say 'I.'"

Our "I" is the only lock on the door to truth. If you break that lock, suddenly you realize that the door was always open.