When we received the life of Christ at salvation, we became one with Christ. The reason the church is called the Bride of Christ is because the moment we got born again, we became one with Christ. However, our becoming one with Christ happened once legally but experientially, we are becoming one with Christ daily. It's the same way we get married in the court/church and the court/church declares you and your husband joined together as one. However, you continue to learn to live as one as you move on in marriage.