1 Peter 1:13 tells us to be conscious of what we are thinking about and be diligent about redirecting thoughts that stray outside the lines of Philippians 4:8.
New International Version (NIV)
8 Finally, brothers and sisters, 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.