"For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; of the Jew first, and also to the Greek. For therein is the righteousness of God revealed from faith to faith: as it is written, The just shall live by faith."
Faith in God begins with believing that when God sent His son, Jesus Christ to die on the cross at Calvary, His death paid the debt for our past, present and future sins. And by His grace alone, we can enter the Kingdom of God. Our faith now turns to living our life for Jesus Christ. Jesus Christ was sinless while He was on earth. We are born sinners and thus cannot live a sinless life. That does not excuse us from sinning. Once you believe that Jesus Christ is your personal savior, you no longer under the law of sin.
"For sin shall not have dominion over you: for ye are not under the law, but under grace."
God knows that we are sinners and thus His judgment will not be whether or not we are perfect in this life. We will be judged on whether or not we believe that He is our Lord and Savior and that His Son's death on the cross paid our sinful debt. We will though, be held accountable for what we do with our life and are we doing everything for the glory of God. As a believer, we have a responsibility to live a holy life.
"I beseech you therefore, brethren, by the mercies of God, that ye present your bodies a living sacrifice, holy, acceptable unto God, which is your reasonable service."