It's not who we are, it's Whose we are.
In Galatians 3 Paul picks up on the theme of blessing and curses based on obedience to the Mosaic Law. Paul shows that righteousness does not come by the Law and he gives the example of Abraham (Gen 15:6), which predates the Law and circumcision (Gal 3:6). Paul's aim here is to show that Christians are blessed like Abraham, not because of what they do, but because they are heirs of Jesus to the blessings of God, through faith in Jesus (Gal 3:9). Paul goes on in 3:10 to quote Deuteronomy 27:26 that pronounces a curse on anyone who does not do "everything written in the Book of the Law." Those who say they are righteous because of their obedience to the Mosaic Law, must obey it perfectly in order to be righteous, whereas those who live by faith in Jesus Christ claim His righteousness. Christ took the curse of humanities disobedience to the Law on himself so the blessings of Abraham could be given, through receiving the Spirit, to those who put their faith in Jesus (Gal 3:13-14). Paul sees Jesus as the fulfilment of the Prophets who foretold that God would initiate the redemption of humanity (Jer 31). This was achieved through Jesus Christ who took the curse on himself so those who believe in Him could receive the blessings promised to Abraham, by faith.
Just as Israel was unable to perfectly keep the Mosaic Law, we fail to remain faithful to God. Our relationship with Jesus, by faith, is what enables us to stand before God, justified and righteous. It is therefore not who we are and what we do that makes us righteous, but Whose we are and who we depend on for our righteousness.