Concerning sin and believers, are we not supposed to stop sinning and keep the Ten Commandments close to us because Jesus says the greatest of the two Commandments is to obey God?
Christians are only required to obey the moral laws in the Old Testament. This includes the Ten Commandments. But we are no longer under the law. We are under grace (Romans 6:14). Jesus perfectly fulfilled the law (Matthew 5:17-20).
When we come under his grace, we are only responsible to obey the commandments and teachings of Jesus. Through the power of the Holy Spirit dwelling in us, as we obey the Holy Spirit, we fulfill the law through Jesus.
If you are referring to the two greatest commandments, the first is to love the Lord your God with your whole being. The second of the greatest commandments is to love your neighbor as yourself. We also follow these through Jesus’ grace and the Holy Spirit’s power.
The Bible makes a distinction between momentary sin for Christians and a continuous lifestyle of sin (1 John 6-10). Christians are not permitted to live a lifestyle of sin and follow Christ at the same time. But they do have momentary sins that they must ask for God’s forgiveness through confession.
No one is perfect. Even Christians walking the path of Christ have momentary lapses into sin. But the goal for Christian living and holiness is to follow Christ without sinning regularly. This isn’t a work we can do ourselves. It is the Holy Spirit’s power in us when we obey him.