Many Christians end up thinking that the goodness they possess doesn't really belong to them -- that it's only Jesus being good within and through them that counts; as if Jesus dwells within them, but alongside a still faithless or tainted heart.
They assume that they themselves couldn't possibly be good: It's just Jesus indwelling that makes them so. The hope is that they're simply banking on Jesus' righteousness within them: because all the faithfulness and purity appears only on Jesus' side of the ledger and none on their side.
While our goodness is exclusively the gift of Jesus to us, and must always be the result of grace, his goodness has become our actual goodness. That's the point of the New Covenant.
The Old Covenant system of sacrifices could not do two things:
1. It couldn’t take away a person’s sin or wash the guilt away.
2. The Old Covenant sacrifices could only lend the person a temporary and outward righteousness:
“The blood of goats and bulls and the ashes of a heifer sprinkled on those who are ceremonially unclean sanctify them so that they are outwardly clean. How much more, then, will the blood of Christ, who through the eternal Spirit offered himself unblemished to God, cleanse our consciences from acts that lead to death, so that we may serve the living God.”
“The law … can never, by the same sacrifices repeated endlessly year after year, make perfect those who draw near to worship. If it could, would they [the sacrifices] not have stopped being offered? For the worshippers would have been cleansed once for all, and would no longer have felt guilty for their sins.” “…because it is impossible for the blood of bulls and goats to take away sins.” (Heb. 10: 1,2,3,4)
Under the old way of relating to God, the worshippers borrowed righteousness through the sacrificial system, but it never really made them righteous. Because of your union with Jesus, his goodness has become your goodness.
We have shifted from borrowed to actual.