The Cross has done all that is needed
"If the cross has done all that is needed, if God has revealed in the Old Testament that human effort is futile, there is no place for man’s effort and accordingly for man’s extolling of his own effort. In any religion of law the worshipper may legitimately feel satisfaction in his personal achievement, but this is a satisfaction that can lead to pride. For those saved by grace, however, that is impossible. Grace leaves no place for satisfaction in one’s own achievement, for salvation is all of God." - Leon Morris, commentary on Romans 3:27.
We wrestle with this reality in life. Each new discovery or improvement, moving up the sanctification ladder, provides fuel for the monster of self-sufficiency. But for those saved by grace, this is impossible. No pride. Just the astonishment that all that was needed to have a relationship with God, to be an heir, a child, was done on the cross by Christ.
It changes our perspective and transforms our hearts. It is all of God. And this is good news.