If Jesus' righteousness is credited to us, as our own---is the complete story---then why are all mankind judged according to their own works--after death--and that for life or damnation?
John 5:28-29---King James Version
28 Marvel not at this: for the hour is coming, in the which all that are in the graves shall hear his voice,
29 And shall come forth; they that have done good, unto the resurrection of life; and they that have done evil, unto the resurrection of damnation.
Matthew 16:27----King James Version
27 For the Son of man shall come in the glory of his Father with his angels; and then he shall reward every man according to his works.
The scriptures do teach some things about the perfection process:
1) That God Redeemed all of mankind from the condemnation of the Fall, through His Atonement and Resurrection--as a free gift to all men:
Romans 5:18---King James Version
18 Therefore as by the offence of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men unto justification of life.
Now--we answer for our own choices--and not Adam's choice--as John5:28-29 shows, although eternal life, as an opportunity for all men--was purchased by Christ alone--as a free gift to all men.
2) Those who walk in the light(faith in Christ))--are Redeemed from their own personal sins--through the Blood of Christby grace are ye saved)
1 John 1:7---King James Version
7 But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin.
That "walk in the light" has integral components which make it up, IE--repentance and water baptism for the remission of sins, keeping the commandments, taking care of the poor, enduring to the end, following the Spirit, etc.(faith in Christ)
3) Our doing of those things which God commands--are righteous acts, and doing righteousness(walking in the light)--contributes to our personal righteousness:
1 John 3:7----King James Version
7 Little children, let no man deceive you: he that doeth righteousness is righteous, even as he is righteous.