Roy Hession puts it so clearly in his book “When I Saw Him”:
If you are still mourning and blaming yourself it is not because God is blaming you; He has put the blame on Jesus. It can only be due to one of two things. Either that you have not really repented, or, more likely, you are mourning over your lost righteousness. Perhaps you feel that, having been saved for so long, you should not be failing as you are. . . . You are in effect saying, “Alas for my lost righteousness.” That is nothing but pride.
Jesus has taken our blame, the charge against us, the sting of our failure. Then why are we so sick about our failure? Because we thought we were better. We regret that our “report card” does not show all the “good marks” we want others to see.
But all the best marks of our own righteousness can only amount to “filthy rags” as the prophet Isaiah says in Isaiah 64:6. They will never be anything we want to showcase. The only righteousness worthy of displaying is the righteousness of Jesus that we have through His powerful and precious blood.
If what we hang on to is filthy rags, why grasp for it anymore? Why mourn over the loss of it? Will we be like the criminal who until the very end esteemed and held on to “his own righteousness,” although obviously it was nothing to boast in?
Paul sums it up in the book of Philippians:
I consider everything a loss compared to the surpassing greatness of knowing Christ Jesus my Lord, for whose sake I have lost all things. I consider them rubbish, that I may gain Christ and be found in him, not having a righteousness of my own that comes from the law, but that which is through faith in Christ—the righteousness that comes from God and is by faith (3:8–9).
Let us leave our rags behind and hold on to His riches.