Bottom line: I am who God says that am. And who He says I am is determined by my faith in the Gospel message.
Paul writing the Corinthians said that if any man be in Christ he is a new creation; the old things pass away and all things become new. One of the new things is a new identity. We are made alive in Christ, become a child of God, set free from the penalty of sin, and receive the mercy of God.
To live out who we are in Christ we need to have faith in what God's Word says about who are in Christ. We need the love of other believers. The Christian experience is to be lived out in community. And we need to have the right confession about who we are in Christ.