Romans 8:12 in the J. B. Phillips says, “…to live life on the level of the instincts. Indeed that way of living leads to certain spiritual death. But if on the other hand you cut the nerve of your instinctive actions by obeying the Spirit, you are on the way to real living.”
Ephesians 4:22, 24 says, “That you put off, concerning your former conduct…and that you put on the new man which was created according to God, in true righteousness and holiness.”
Medical surgery can cut a nerve that renders a part of the body useless and non functioning. God’s scalpel, the word, is so precise that He is able to split between our soul and spirit, and discern our thoughts and intentions. When we walk in the Spirit, we are walking in the truth of God’s word. It is always at work to discern our thoughts before we think them.