The human brain is "plastic". It can change and mould itself according to what it is exposed to. Pornographic material is one of the major causes of fucked-up mental stability and pleasure systems in your body. The instant form of gratification through porn really messes with your neurotransmitter "Dopamine" due to which you experience side-effects like over-anxiousness, bad self-image, stress, lack of motivation or desire. Although you can rewire your brain again to its natural state. 
Listen to this episode of THE MODERN MONK SHOW to learn more about how 'pornographic material' and 'masturbation'  badly affects your mind and body and how you can overcome with the 'addiction'.