The law of Jesus in our hearts is the new covenant. Instead of going to the written law to find out what is right, we go directly to Jesus. As we are led by his Spirit every day, He gives our physical bodies life. We don't have to sin just because we live in a flesh body. We choose whether to consecrate our bodies to Jesus, or to the law of sin and death.
Do you believe, “I just have to do my best, but I'm still going to sin?” If so, you're walking under the law and not in salvation. When God supernaturally writes the law of Jesus in your heart, you will keep it. By the power of the Holy Spirit, you will stop sinning and do what Jesus tells us to do. Salvation is this daily walking out of the new covenant. Those who will inherit eternal life walk now, daily, under the anointing and power of the Holy Spirit. Are you living under the old covenant, or the new?