Romans 12:1 I beseech you therefore, brethren, by the mercies of God, that you present your bodies a living sacrifice, holy, acceptable to God, which is your reasonable service.
A battle starts to take place in your mind as soon as you become a Christian, because the enemy wants to get back what he has lost. The Holy Spirit wants to keep what has been accomplished. The satanic forces will put thoughts into your mind that are contrary to what the Lord wants you to think. You have to decide whose thoughts you are going to accept.
The mind of each one of us has a controlling factor, which is the spirit of the mind, and must also be renewed by the power of the Holy Spirit, see Ephesians 4:22-32. God wants to renew your mind, to remove the contamination that could have filtered in by being in contact with the world. Allow yourself to be “washed” in the Word daily. The closer you get to Him, the less of the world will stick.