If your eye is healthy, your whole body will be full of light.
What we are has much to do with how we see. A person who is a pessimist will see difficulties, whatever the picture. An angry person will see reasons to fight regardless of the circumstance. A compassionate person will see opportunities to show kindness whenever he meets a new person. A godly person will perceive God's hand in every situation.
How we perceive either condemns or commends us. How we perceive brings us either to Glory or to perdition.