From The Vanishing Conscience by John MacArthur, page 224.

For the Christian, the life of slavery to sin is past.  Sin cannot continue to be the chief characteristic of our lives.  Fleshly disobedience interrupts the new life frequently and we do sin.  At times sin may appear to dominate a Christian’s life completely (as was the case when David sinned).  But all true believers still have a new and holy nature. They hate their sin and love righteousness. They cannot live in unbroken sin or hardened rebellion against God and enjoy it. That would be a contradiction of who they are (cf. I Jn. 3:9).