We are nobly or ignobly changed by what we contemplate. The love of God cannot compete with cheap jazz, cheap reading, cheap and vulgar jokes, vulgarly suggestive and low entertainment. Blessed are the pure in heart, for they shall see God. That is just it. It takes that kind of mind to see God, to desire and enjoy God.
Impurity always replaces itself with impurity.
Fear never replaces itself with love. Error never replaces itself with truth. Vulgarity never replaces itself with Christian refinement. Jesus dispels our darkness of mind. In His presence it is really difficult to be mean, cruel, hostile, selfish, unclean, or vicious.