There is a person in the Bible who lived in mental torment because he sincerely tried to adhere to the Ten Commandments.
The more he tried to obey them, the more he disobeyed them.
He was in mental torment because the law he loved and tried to live by sentenced, or condemned, him to death.
He asked who could rescue him from this condemnation.
He then gave thanks to God for Jesus who took his condemnation.
Consequently, there was no more condemnation for this man because he placed his faith in Christ and was in Christ.
Through faith in Christ he was freed from the law of sin and death.
He no longer was in mental torment because his mind was no longer fixed on the Ten Commandments.
He experienced mental peace because his mind was now controlled by the Spirit of Christ.
The Spirit of Christ in us fixes our mind on grace, not the law.
Therefore, we are at peace because we don't live in fear of condemnation for having disobeyed the Ten Commandments, since Jesus took our condemnation.
By faith in Jesus, we are at peace with God, we are justified, innocent of having broken the Ten Commandments and stand before God righteous.
We now stand in grace, no longer relating to God by the Ten Commandments, but relating to him as Abba Father.
To read more about the man in the post see Romans 7:7-8:3. Also, read Romans 5:1-2.