What it is that keeps a fool from being wise:

His way is right in his own eyes; he thinks he is in the right in everything he does, and therefore asks no advice, because he does not apprehend he needs it; He is confident he knows the way, and cannot miss it, and therefore never enquires the way. The rule he goes by is to do that which is right in his own eyes, to walk in the way of his heart. Quicquid libet, licet - He makes his will his law.

He is a fool that is governed by his eye, and not by his conscience.

What it is that keeps a wise man from being a fool; 
He is willing to be advised, desires to have counsel given him, and hearkens to counsel, being diffident of his own judgment and having a value for the direction of those that are wise and good. He is wise (it is a sign he is so, and he is likely to continue so) whose ear is always open to good advice.

Matthew Henry commentary

[ Emphasis Mine]