In my opinion, one of the many key verses to keep in focus when discussing repentance, faith, salvation... (beside the one about Godly sorrow) is found in Ga 2:20
I am crucified with Christ: nevertheless I live; yet not I, but Christ lives in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me.
Within this single verse is the personal work of the believer to "crucify" not only the fleshly, but also it shows the important truth that Christ died for the believer's sins.
Secondly, is the life lived in the flesh is to be a life of faith; but NOT faith that is MAN generated, for such faith is faulty, frail, and bound to fail.
Third, the faith is "by" which in the original is not a word that signifies any movement such as one might "come to Jesus." Rather, it is a significant word which indicates ownership of or title holding. I often use the illustration of cars ownership. What is the single indicator demarcating all other cars from "your" car? The title.
Fourth, the faith is the faith of Christ. PLEASE be very careful to recognize that the work is all of Christ. The verse isn't saying faith "in" but faith "of the son" which in the original is "huios" which indicates kinship. Fifth, the verse shows the purest form of love.
Repentance is important; it is vital to becoming the believer and sustaining victory as a believer.
However, sorrow generated of this world only leads to destruction; however, "Godly sorrow (that which only God can bring by Holy Spirit conviction and believer salvation) works (katergazomai - fashions, forms, accomplishes) repentance unto salvation." 2 Cor. 7:10
Great thread, FAL!