We have not just been justified. We have been also reconciled. Ever hear someone say, "I'll forgive, but I won't forget." Maybe they are sincere. Maye they are correct. That means while, they do not hold onto the offense, there is still no peace in the relationship. They have given up any claim for "payment" for the offense, but they do not want to touch hearts with the person. God has given up his rights for restitution. He also seeks to connect in a love relationship, and give blessings. He chooses to treat us as if we never sinned.
I am not saying people do not sin. I am saying that in his relationship with his children, God treats them as though it never happened. I sure this opens up a theological can of worms. Someone might say that we do not treat sin seriously enough. But I don't think we realize how far God goes in dealing with man's sin and rebellion. I don't think we realize how big grace is.