The mind is the battlefield for the devil. That is where he attacks you and tempts you and lies to you. Perhaps that is why the apostle Paul was so adamant about guarding your thoughts.
Phil 4:8 – 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.
2 Cor 10:5 – Take every thought captive to obey Christ
Rom 12:2 – Be transformed by the renewing of your mind
Rom 8:6 – For to set the mind on the flesh is death, but to set the mind on the Spirit is life and peace
Be careful, “Your enemy the devil prowls around like a roaring lion looking for someone to devour.” He is looking for unguarded minds that he can tinker with. Be sure that you are consciously focusing on Christ today and replacing thoughts that do not honor Him.