The Law, God's Word is in the heart, Mind and mouth through Christ. We are a new creation in Christ Jesus. If we are not living according to the change that He has done in us we are denying Christ and are not saved anymore.
Believers are new creations in Christ and if we claim to be saved, yet there is no change in us at all according to what Christ does in us, then we are not saved to begin with and never were.
Romans 10:5 - For Moses writes about the righteousness which is of the law, "The man who does those things shall live by them." 6 But the righteousness of faith speaks in this way, "Do not say in your heart, 'Who will ascend into heaven?' " (that is, to bring Christ down from above) 7 or, "Who will descend into the abyss?" (that is, to bring Christ up from the dead). 8 But what does it say? "The word is near you, in your mouth and in your heart" (that is, the word of faith which we preach): 9 that if you confess with your mouth the Lord Jesus and believe in your heart that God has raised Him from the dead, you will be saved. 10 For with the heart one believes unto righteousness, and with the mouth confession is made unto salvation. 11 For the Scripture says, "Whoever believes on Him will not be put to shame."