Every Christian is at war. There is a perpetual struggle against Satan and his kingdom where there are no "leaves" or "discharges." Our enemy goes about as a roaring lion, seeking whom he may devour (1 Peter 5:8). Those who resist the devil will see him flee (James 4:7). The only ones whom he devours are those who don't actively fight against him.
The mind is the battlefield where thoughts and reasonings that are contrary to God's Word, need to be captured and submitted to Christ, our Commander.
Our rebel thoughts must be taken captive and made to submit to Christ. Our battle against the devil takes place right between our ears. The spiritual weapons given to us are designed for the purpose of taking EVERY thought captive and making them obedient to Christ. Keeping our minds completely stayed upon the Lord is an obtainable goal.
These weapons of ours are for the casting down of two things: Imaginations; and every high thing that exalts itself against the knowledge of God. Both of these areas are dealing with the mind. Focus on the good in every area of your life. Failure to recognize God's blessings in every day living will cause care and anxiety. Recognizing God's hand in even the smallest thing will cause peace and keep our hearts and minds following hard after the Lord.