Because Christ has come to this earth, died and rose again, people are born "in Him", not because of what people did, but because of what God through Christ has done for them. Jesus the bread of life came to this world to give it life (John 6:33). Obviously, the world is dead otherwise He would have not given it life. That's why He said that no one can come to Him except the Father draws him (John 6:44).
So, on the cross, the Father fashioned Jews and Gentiles (humanity) into the body of His Son, creating a new man on the cross: The Son is the Head, humanity the body (Eph 2: 11-19). When His Son the Head, died, humanity - His Body - died (2 Cor 5:14, 15). When the Head resurrected, the body was made alive together with Him (Col 2:13; Eph 2:4-6), born again into a living hope through the resurrection of Jesus (1 Pet 1:3).
Now that we all are alive, we can do spiritual things like believing, repenting, etc., which can be summarized simply into overcoming evil with good (Rom 12:21). Believing is overcoming the evil of unbelief; repentance is overcoming the evil of impenitence. Being "in Christ", we are attached to Him Who is our Strength for overcoming evil (Phil 4:13). And overcomers will not be blotted out from the book of life (Rev 3:5).