"Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new." -- 2 Corinthians 5:17
Having faith (faith is a gift of God) in Christ is the only way a person can attain righteousness. For it is by faith that the righteousness of Christ is imputed unto us (Romans 4:4-6, Romans 4:20-24). And it is by grace through faith that we are saved, not of our own works (Ephesians 2:8-9). The only way we can inherit the kingdom of God is to be born again. Being born again is a complete, and supernatural work of the Holy Spirit, of God working in, and through you. One of the many evidences of someone's faith is that they will bear good fruit. Not the fruit of your own flesh, but the fruit of the Spirit. "But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith, Meekness, temperance: against such there is no law." -- Galatians 5:22-23
People typically confuse the grace of God, and think, because we are no longer under the Law (2 Corinthians 3, Romans, Galatians, and Ephesians) that we can still act in carnality. But what they fail to realize is that the evidence that you've been saved is that the Holy Spirit of God is working in and through you. How can someone filled with the Holy Spirit of God lead a life full of carnality? Is the Holy Spirit of God carnal? God forbid. When you are born again, you will walk in the newness of life, and of the Spirit -- not in the oldness of which once was.
"Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death? Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life. For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection: Knowing this, that our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin." -- Romans 6:3-6