Watch over your heart with all diligence, for from it flow the springs of life. Proverbs 4:23 NASB
How do we watch over (guard) our hearts? Use the Philippians 4:8 filter to frisk every thought that enters our mind: Is it true (is it consistent with the Word of God)? Is it noble? Right? Pure? Lovely? Admirable? Excellent? Praiseworthy? If the thought fails any one of these tests, don’t let it in.