My daughter has her G1, which means she is just learning how to drive. Eventually she will graduate into her full G license at which point there will be no driving restrictions other than obeying the law. She is learning through a friend that if you choose to break the law, you may be fined, and she knows that if you break the law severely enough, you may lose your license.
Of course, the decision to follow the law is completely up to her. She could decide that having her full license makes her free to drive however she wants to, but she would be wrong. If she breaks the law, whether or not she gets caught, she is still breaking the law. With that attitude, she will always be at risk of the consequences of her decision. There isn't much difference between a law breaking driver and a Christian who thinks that God's forgiveness means they can continue to sin.
What shall we say then? Shall we continue in sin so that grace may abound? Let it not be! How shall we who died to sin live any longer in it? Rm. 6:1,2For sin shall not have dominion over you, for you are not under Law, but under grace. What then? Shall we sin because we are not under Law, but under grace? Let it not be! Rm. 6:14,15
For if we sin willfully after we have received the knowledge of the truth, there remains no more sacrifice for sins, Hb. 10:26
God doesn't give us permission to sin just because we are forgiven. In fact, He wants us to be holy as He is holy (1Pt. 1:16). He wants us to "Hate the evil, and love the good..." (Am. 5:15). If we truly love Jehovah, then we will hate evil (Ps. 97:10), for God is love (1Jh. 4:8) and love should be without hypocrisy- abhorring that which is evil and cleaving to that which is good (Rm. 12:9 KJV).
We are surely saved by grace through faith in the finished work of Jesus Christ, and not by works. But repentance is a part of turning to Christ and includes a change in heart and ways. If we are truly repentant, then we will not want to sin and will try to live as dead to sin; we will try to live holy lives. In fact, the way we live after salvation should show continual changes for the better in us.
Some of the words involved in these changes are: sanctification, transformation, renewed, etc. There are at least two ways the world knows we are Christians: by our love (Jh. 13:35) and by showing fruits in our lives (Mt. 7:16-20). And just like a driver's license, if we choose to break the law (sin) then there will be consequences. Perhaps it builds a wall between the Lord and us, or we have an unmarried pregnancy, lose a relationship, never break out of the devil's bondage, etc. Whether or not we pay those consequences now or later, they will be paid for.
How we live is our decision!