I don't see why it's so hard to understand that if you say a person is saved by grace but "kept" saved by their works (like abstaining from sinning) it is no different than saying a person is saved by their works (being good, not sinning, etc.). Grace means undeserved, unmerited favor and, by definition, whatever is offered by grace cannot then be merited or deserved. Over and over we are told in Scripture that God saves us by his mercy and grace so who are we to come along and shove his gift back in his face insisting that we CAN earn, merit or deserve it?
This has nothing to do with our goodness because, compared to the holiness and righteousness of God, all we can muster up is comparable to filthy rags. We are saved by grace because it HAD to be grace. No amount of good works, deeds, efforts can pay the penalty of sin because God said "blood makes an atonement for the soul" (Lev. 17:11). He made us and he made the rules. It's his way or hell - and that ain't the highway!
7Know then that it is those of faith who are the sons of Abraham. 8And the Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel beforehand to Abraham, saying, "In you shall all the nations be blessed." 9So then, those who are of faith are blessed along with Abraham, the man of faith.