Unless we believe the gospel, we will be driven in all we do-whether obeying or disobeying-by pride ('self-love') or fear ('of damnation'). Apart from 'grateful remembering' of the gospel, all good works are done then for sinful motives. Mere moral effort may restrain the heart, but does not truly change the heart. Moral effort merely 'jury rigs' the evil of the heart to produce moral behavior out of self-interest. It is only a matter of time before such a thin tissue collapses.
Timothy Keller