The decision and action that we make in daily come from what our heart say within. Therefore, we have to keep our hearts so that it only produces good messages. How? by controlling any things that are properly put into our heart.
A good man brings good things out of the good stored up in his heart, and an evil man brings evil things out of the evil stored up in his heart. For the mouth speaks what the heart is full of. (Luke 6:45)