Jesus said in His sermon on the mount, "The eye is the lamp of the body. If your eyes are healthy, your whole body will be full of light." It's amazing how our mind is easily corrupted when evil images get in.  These images imprint and affect our hearts. The flesh is an enemy that the Christian must deal with in order to survivie. Thankfully we are not alone, because we have the Holy Spirit to aid us in our war against the Works of the Flesh.