Try a simple explanation.
Extrinsic Justification. This is justification by grace alone the doctrine of extrinsic justification and the rejection of the Catholic view of faith formed by charity as “saving faith.” Extrinsic justification is the idea that justification occurs outside of man, rather than within him. The Reformers, like the Catholic Church, insisted that justification is by grace and therefore originates outside of man, with God. But they also insisted that when God justifies man, man is not changed but merely declared just or righteous. God treats man as if he were just or righteous, imputing to man the righteousness of Christ, rather than imparting it to him. Calvin tried to circumvent the biblical problems of the extrinsic justification theory by positing a systematic distinction between justification, which puts us in right relation to God but which, on the Protestant view, doesn’t involve a change in man; and sanctification, which transforms us. Yet this systematic distinction isn’t biblical.
Intrinsic Justification. Catholicism holds that justification is by grace alone. In that sense, it originates outside of man, with God’s grace. But, according to Catholic teaching, God justifies man by effecting a change within him, by making him just or righteous, not merely by saying he is just or righteous or treating him as if he were. Justification imparts the righteousness of Christ to man, transforming him by grace into a child of God. There is neither a logical nor a biblical reason why God cannot effect a change in man without undercutting justification by grace alone. Whatever righteousness comes to be in man as a result of justification is a gift, as much any other gift God bestows on man. Nor does the Bible’s treatment of “imputed” righteousness imply that justification is not imparted. On these points, the Reformers were simply wrong:
There is no doubt that grace, for St. Paul, however freely given, involves what he calls ‘the new creation’, the appearance in us of a ‘new man’, created in justice and holiness. So far from suppressing the efforts of man, or making them a matter of indifference, or at least irrelevant to salvation, he himself tells us to ‘work out your salvation with fear and trembling’, at the very moment when he affirms that ‘. . . knowing that it is God who works in you both to will and to accomplish.’ These two expressions say better than any other that all is grace in our salvation, but at the same time grace is not opposed to human acts and endeavor in order to attain salvation, but arouses them and exacts their performance."
In the Bible, justification and sanctification–as many modern Protestant exegetes admit–are two different terms for the same process. Both occur by grace through faith and both involve a faith “informed by charity” or completed by love. Faith in the Pauline sense, “supposes the total abandonment of man to the gift of God”–which amounts to love of God. He argues that it is absurd to think that the man justified by faith, who calls God “Abba, Father,” doesn’t love God or doesn’t have to love him in order to be justified.
So with this in mind if someone offered you the opportunity to be declared righteous or to become righteous which is most appealing. Put it another way. If you are a Catholic and accept being declared righteous, are righteous are a child of God really and truly to become Protestant means you have to give this notion up and become a creature declared innocent and not be truly righteous just be declared righteous. Both are on account of the righteousness of Christ.
I like being a child of God, not an acquitted criminal, given the grace to please God and then getting rewarded by my Father and I don’t deserve it and I didn’t earn it, reminds me of my daddy…