The work on the cross is complete. Jesus accomplished what he was sent to do. Forgiveness, reconciliation and restitution have been provided freely to us. God has given us everything we ever had that was good, including life itself. As such we are debtors who could not possibly repay the debt because we have nothing to pay with.
Jesus opened a door (the door out of Satan and sin's jaol) and set us free.
In my imagination I see a window between heaven and earth. This window is Jesus. When we try to look into heaven to see God, we see Jesus. When God looks at believers in Christ on earth, he sees Jesus. We have been clothed in righteousness, and Jesus is our righteousness. I think Isaiah's words apply to us:
Isaiah 61:10 (RSV)
I will greatly rejoice in the Lord,
my soul shall exult in my God;
for he has clothed me with the garments of salvation,
he has covered me with the robe of righteousness,
as a bridegroom decks himself with a garland,
and as a bride adorns herself with her jewels.
Then I think of the state I'm really in, one of continued conflict between my old and new selves, and I realize that I have a long way to go before I fill this "robe of righteousness." Righteousness is something you DO, you PRACTICE. A person who does nothing cannot claim to be righteous. Faith also is an action word, in fact. It is one side of a coin - the other side is "obey." As in Trust and Obey.
God did not only free us from sin and death to go out and "be righteous" He has also prepared a program of activities and behaviours, and specific "works" for each of us, individually and as a Body as in:
For we are his workmanship, created in Christ Jesus for good works, which God prepared beforehand, that we should walk in them.
We are not saved by our works, we are saved FOR our (actually HIS) works. And we can only do them because of the atonement of Christ, and when we subsume our daily wills to his, letting Him act through us. Without Him we can do nothing. With Him, all things are possible! We have to start growing in the Lord so that we will eventually fit those robes of rigtheousness.