"Has forgiven you" is too weak a term.
"Highly favored you" or "greatly graced" you is much more appropriate, yet even then we cannot begin to describe how greatly God our Daddy has graced us through His Son Jesus!
"And you, being dead in your sins and the uncircumcision of your flesh, hath he quickened together with him, having forgiven you all trespasses;" (Colossians 2: 13)
Paul was clear. Don't water it down: "all trespasses". Every sin!
John was emphatic with unbelievers in his First Epistles:
"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." (1 John 1: 7)
The blood of Jesus cleanses, present tense.
Jesus is also our High Priest Forever:
"Whither the forerunner is for us entered, even Jesus, made an high priest for ever after the order of Melchisedec." (Hebrews 6: 20)
"For the law maketh men high priests which have infirmity; but the word of the oath, which was since the law, maketh the Son, who is consecrated for evermore." (Hebrews 7: 28)
Why does this eternal status of Jesus our High Priest matter? The fullness of the New Covenant means nothing without the full assurance of Jesus' work at the Cross:
"10For this is the covenant that I will make with the house of Israel after those days, saith the Lord; I will put my laws into their mind, and write them in their hearts: and I will be to them a God, and they shall be to me a people:
11And they shall not teach every man his neighbour, and every man his brother, saying, Know the Lord: for all shall know me, from the least to the greatest.
12For I will be merciful to their unrighteousness, and their sins and their iniquities will I remember no more." (Hebrews 8: 10-12)
Not only does God no longer remember our sins no more, but He now is committed to blessing us, to being our God, to guiding us from within, and caring for us without.
So, now we return to Paul's exhortation: "Be gracious, even as God for Christ's sake has been gracious to you."
He not only forgave our sins, but gave us new life. He not only forgave all our sins, but has blessed us with all spiritual blessings in Christ Jesus (Ephesians 1: 3)
God became a gainer through Jesus' death on the Cross, and even when we sin (verb) the grace of God superabounds in our lives to this day (Romans 5: 20)
With the understanding of our great and gracious our God is because of His Son, we can understand this prophecy:
"1Sing, O barren, thou that didst not bear; break forth into singing, and cry aloud, thou that didst not travail with child: for more are the children of the desolate than the children of the married wife, saith the LORD." (Isaiah 54: 1)
Jesus has overpaid our debt, allowing us to be blessed in Him. Rejoice!