Therapeutic?
You mean Jesus blood isn't enough to cleanse us from all sins after all?
That temporal punishment is due to sin, even after the sin itself has been pardoned by God, is clearly the teaching of Scripture. God indeed brought man out of his first disobedience and gave him power to govern all things (Wisdom 10:2), but still condemned him "to eat his bread in the sweat of his brow" until he returned unto dust. God forgave the incredulity of Moses and Aaron, but in punishment kept them from the "land of promise" (Numbers 20:12). The Lord took away the sin of David, but the life of the child was forfeited because David had made God's enemies blaspheme His Holy Name (2 Samuel 12:13-14).
In the New Testament as well as in the Old, almsgiving and fasting, and in general penitential acts are the real fruits of repentance (Matthew 3:8; Luke 17:3; 3:3). The whole penitential system of the Church testifies that the voluntary assumption of penitential works has always been part of true repentance and the Council of Trent (Sess. XIV, can. xi) reminds the faithful that God does not always remit the whole punishment due to sin together with the guilt. God requires satisfaction, and will punish sin, and this doctrine involves as its necessary consequence a belief that the sinner failing to do penance in this life may be punished in another world, and so not be cast off eternally from God. [1]
[1] Hanna, E. (1911). Purgatory. In The Catholic Encyclopedia. New York: Robert Appleton Company. Retrieved October 16, 2014 from New Advent: http://www.newadvent.org/cathen/12575a.htm