10 For it is with your heart that you believe and are justified, and it is with your mouth that you profess your faith and are saved. Romans 10:10
We are justified by faith alone. It is not a result of our works. Our works are a result of authentic faith and an authentic relationship with Jesus Christ. It is impossible to claim that you follow Jesus Christ yet fail to be transformed into His image. An easy litmus test to determine if we are truly in Christ is the fruit of the Holy Spirit in our lives.
If we are truly walking with Christ on a daily basis and seeking Him through prayer and His word, we will be supernaturally transformed from the inside out through the power of the Holy Spirit. When we come to Christ we receive the Holy Spirit and are born again. It is the work of the Holy Spirit within us that transforms us. We are not transformed or changed by our own strength or power. In ourselves we are weak and feeble and if we try to accomplish anything in our own strength we will simply fail.
But the Lord has called us simply to believe. To place our faith and trust in Him and to abide in Him on a daily basis. To set aside the deeds of darkness and be transformed into the image of Christ. The more we spend time with Him and yield our hearts and lives to His will, the more we become like Jesus in every way.