“Mine eye affecteth mine heart because of all the daughters of my city.”
Your heart refers to your internal make up: your spirit, will, mind, and emotions.
Faith is a product of the spirit and both faith and unbelief can be provoked by sight. When Jesus died and resurrected, Thomas only believed when he saw him.
What you see also has an effect on your emotions. For example, you will experience fear if you were to see a snake in your bedroom. Why will you be afraid? Because your eye affects your heart.
Your will can also be influenced by sight. For instance, when you expose your eyes to pornography, it can influence you to commit adultery and fornication. The mind is the center of command and it makes decisions. Your decisions are influenced by what you see. If you will remember, Eve decided to eat of the forbidden tree because it looked good to eat. The result was chaos as we know it today.
Because your eye influences your heart, it is important to consciously filter the images you allow to affect your heart. You must shield your eyes from negative things like pornography, certain types of movies, books and places which project negative images. We must constantly expose our eyes to wholesome things like the scriptures.
Job said in Job 31:1 that, “I made a covenant with mine eyes; why then should I think upon a maid”?