Your mind will determine if you will live a successful Christian life or not. You see, man is a spirit, possessing a soul and lives in a body. Your soul houses your mind, which is where you have your reasoning and emotions. If you are born-again, it is your spirit that is recreated, not your mind. Your mind will still think the same thoughts, your desires will still be the same. You are the one responsible for renewing your mind and this is very important because your mind is the doorway to your spirit and your mind will determine what you say and what you say will determine if you will have a happy or a sad life.(take a deep breathe, read it again:)
The battles of life are fought in the mind. The devil put negative thoughts in the mind, what you see, feel, taste etc can direct your mind too which always go against the will of God for you. This makes the life of a Christian miserable. BUT THANK GOD WE HAVE THE VICTORY! 2 Corinthians 10:4-5 NLT says, "We use God's mighty weapons, not worldly weapons, to knock down the strongholds of human reasoning and to destroy false arguments. We destroy every proud obstacle that keeps people from knowing God. We capture their rebellious thoughts and teach them to obey Christ."
You must fight the good fight of faith! 1 Timothy 6:12. Nobody will fight it for you. Refuse to accept negative thoughts, mind what you read, see, and hear. The Bible says, "Carefully guard your thoughts because they are the source of true life." PROVERBS 4:23 CEV. Christianity is a conscious thing. Make up your mind to follow God's Word. Romans 12:2 NLT tells us, "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."