"that (salvation) [is] not of yourselves, it is the gift of God; not as a result of works, that no one should boast."
Before salvation, man worships at the altar of himself, deciding what is good or bad, true or false by his own sense of right and wrong. However consistently he may or may not live up to his own standard, there is yet the desperate hope that God will accept his attempts at goodness as sufficient for entrance into heaven in the end.
After all, he reasons, nobody's perfect. And God's in the forgiving business. Besides, everyone will eventually get to heaven anyway, right?
What is missed in this vain thinking is the eternal seriousness of sin's consequences in the light of God's absolute holiness.
Not comprehending (much less experiencing) God's perfect holiness, man simply ignores it, preferring to focus on a warped perception of His love, for hope. But this is whistling in the wind. For God is not mocked; neither does His holiness change.
Whatever man may wish, prefer, hope, or speculate, there is salvation in no one but the Lord Jesus Christ. He, and He alone, satisfied by His sinless life and atoning death the righteous requirement of God's holiness affronted. No human deeds, however noble, could possibly earn or deserve the salvation provided freely by the Lord Jesus. To even try is to insult His grace.