The brain is like a tree, bad thoughts are dry branches. Just like how you prune a tree you need to prune your brain.
The Word is the prunning tool. The Word says we change our mind by the washing of the Word. Hebrew 4:12 state ‘For the Word of God is quick (alive) and powerful and sharper than any two-edged sword, piercing even to the dividing asunder of soul and spirit (penetrating to the dividing line of the breath of life (soul) and the imortal spirit) and of the joints and marrow (of the deepest parts of our nature) and is a discerner (exposing and sifting and analyzing and judging) of the thoughts and intent of heart.’
John 15:1-11 Jesus (who is the Word of God) says ‘I AM the true vine and my father is the husbandman. Every branch in me that beareth not fruit he taketh away: and every branch that beareth fruit, he purgeth it, that it may bring forth more fruit. Now ye are clean through the word which I have spoken unto you.Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me. I am the vine, ye are the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing. If a man abide not in me, he is cast forth as a branch, and is withered; and men gather them, and cast them into the fire, and they are burned. If ye abide in me, and my words abide in you, ye shall ask what ye will, and it shall be done unto you. Herein is my Father glorified, that ye bear much fruit; so shall ye be my disciples…’
We control our thoughts by using our tongue. When we control our thoughs we can control our body. James 3:2 For in many things we offend all. If any man offend not in word, the same is a perfect man, and able also to bridle the whole body.