Mark 7:14-15

After He called the people to Him again, He began saying to them, “Listen (carefully) to Me, all of you, (hear) and understand (what I am saying): there is nothing outside a man (such as food) which by going into him can defile him (morally or spiritually):  but the things which come out of (the heart of) a man are what defile and dishonor him.  

Keeping our hearts focused on what is pure and lovely is essential.  We need to be diligent in what we hear and come before our eyes to persuade us or lead us away from the word.  What we believe in our hearts comes out of our mouths and affects the direction of our lives.