Philippians 3: not having a righteousness of my own that comes from the law, but that which is through faith in[a] Christ—the righteousness that comes from God on the basis of faith.
Luther in the reformation emphasized salvation is by faith alone, in Christ alone, through His Word alone. I think this is important in that it whittles away all the unnecessary objects that man can add to salvation, when God has made it so simple and accessible. If you've not considered these things before please search the Bible for the clues of how all humans are forgiven by the sacrifice of Jesus Christ on the cross. Nothing can be added to make us more presentable, for that would be to make Christ lesser, and nothing can be taken away from Christ for it is only by him, and his name by which we may be saved.
For those of you that have understood the wonder of God's forgiveness in Christ, placing you in the family of God, I want to encourage you but reminding you that just as salvation is through faith alone, so also is your perseverance in Christ. You will not persevere based on your past performance or based on your mental resolved, no. You will be able to wake up tomorrow knowing you still reside in the family of God because of God's love to you. His mercies are new every morning and you can persevere another day by him alone. Have faith that he will erase all the sins of your life. The ones in the past, the ones today and the ones yet in your future. Your faith is in Him and in Him is your perseverance.