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. To keep company with Christ is to expose ourselves to that which restores in us His image. In company with Christ we partake of His love, His righteousness, His character.