Renewing the mind is a little like refinishing furniture. It is a two-stage process. It involves taking off the old and replacing it with the new. The old is the lies you have learned to tell or were taught by those around you; it is the attitudes and ideas that have become a part of your thinking but do not reflect reality. The new is the truth. To renew your mind is to involve yourself in the process of allowing God to bring to the surface the lies you have mistakenly accepted and replace them with truth. To the degree that you do this, your behavior will be transformed.
Romans 12:1-2 And so, dear brothers and sisters, I plead with you to give your bodies to God because of all he has done for you. Let them be a living and holy sacrifice—the kind he will find acceptable. This is truly the way to worship him. Don’t copy the behavior and customs of this world, but let God transform you into a new person by changing the way you think. Then you will learn to know God’s will for you, which is good and pleasing and perfect.