It would never occur to you to call a butterfly a 'good looking converted worm.' Why not? After all, it was a worm, and it was 'converted.' It is now a new creature, and you don't think of it in terms of what it was. We, too, were once old sinners and were converted, but that is not what we are today. Visit their marvelous ministry below !
That is why Paul addresses all of his letters to the 'saints' and not to all the 'old sinners saved by grace.' Being a new creature in Christ means that we have a brand-new identity. And this new identity is not determined by how we act.
When we sin today, it is like the Lord brings a huge mirror and places it above us and asks, 'Who are you?' You look up and say, 'A butterfly, Lord.' 'Then why are you crawling around with the worms?'
'I don't know, Lord. It doesn't make much sense, does it?'
And then it's as if the Lord says, 'I didn't make you into a new creature so that you could crawl around like a worm. I made you into a new creature so that you could fly with the butterflies. Get up and fly!' Our identity is now the motivation for our behavior. Paul tells us in Ephesians 5:8, 'You were once darkness, but now you are light in the Lord. Live as children of light.' A good paraphrase is 'Once you were a worm; now you are a butterfly. Fly like a butterfly!' It just makes sense.
( These excerpts are from Bob George's wonderful book entitled 'Classic Christianity' and 'Classic Christianity Illustrated')