Just as we must learn to bring the appetites of our bodies under control, so we must learn to bring our thought lives under obedience to Jesus Christ.  In fact, Paul warns us against misguided and wrongly motivated attempts to control the body that leave our thought lives unrestrained (Colossians 2:23).  It is possible to curb the natural appetites of the body outwardly and yet be filled with all manner of inner defilement.
     The Bible indicates that our thought lives ultimately determine our character.  Solomon said, "For as he thinks within himself, so he is" (Proverbs 23:7).  A old well-known verse puts it this way:

          Sow a thought, reap an act;
        Sow an act; reap a habit;
        Sow a habit, reap a character.

     It is because of the importance of our thought lives that Paul said, "Finally, brothers, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable---if anything is excellent or praiseworthy---think about such things." (Philippians 4:8).
     We have been called to no longer be conformed to the pattern of this world but we are to be renewed in our minds (Romans 12:1-2).  Holiness begins in our minds and works out to our actions.  This being true, what we allow to enter our minds is critically important.