As a Christian you have moved from darkness to light. You have been rescued from the gutter, had a ring put on your finger, a robe around your shoulders. You have moved from being a beggar to becoming royalty. To sin is to return, if only be it for a short time, to being a beggar. Sin (returning to being a beggar) is inconsistent with who you have now become. Why would you want to leave a place of royalty and return to being a beggar? The old has gone the new has come!