The "Good News" of the Bible proclaims that the Cross and resurrection of Jesus Christ has benefited all people, not just some. The Scriptures teach that the reason God sent His Son into this world was to live a sinless life, die on the Cross and be raised from the dead so that you can have new life in Christ Jesus.
Your Sins Have Already Been Forgiven
The Bible teaches that all sins of all people for all time have already been forgiven and forgotten on the Cross of Jesus Christ 2,000 years ago. Only one single sin, the eternal and unforgivable sin of unbelief in Christ as Savior, was not forgiven on the Cross. This single sin of rejecting Christ is the barrier that people place before God and His free offer of salvation unto eternal life through faith in Christ Jesus. All are forgiven but not all are saved because salvation is more than forgiveness.
Being Saved = Being Born Again = Eternal Life in You
Because your sins were already forgiven, something else happens when you trust in Christ as Savior - God removes your old sinful spirit (a.k.a. "heart" or "nature") and replaces it with a brand new, clean heart. Now being a "clean vessel" in your new heart, the Holy Spirit has a place in you to live. His indwelling presence makes you literally righteous because He joins as one with you in spirit. A new heart filled with the Holy Spirit is what Jesus was talking about when He said, "You must be born again." Whereas forgiveness was the necessary first step before God could redeem you, having a new, righteous heart is specifically what saves you. Only the righteous can be saved. You are made righteous in your new heart because the Righteous One lives in you; and, you possess eternal life because Eternal Life now dwells in your heart.
Why Faith is Necessary
Whereas your inner spirit is redeemed and made righteous fully and forever, your outer mortal body has not yet been redeemed. Thus, your spirit is alive because it has been made literally righteous but your physical body is still dead because of sin.
Romans 8:10 If Christ is in you, though the body is dead because of sin, yet the spirit is alive because of righteousness.
Explanation of Romans 8:10 If Christ is in you (this verse is speaking to people who are already saved), though the body is dead because of sin (because your mortal flesh has not yet been redeemed), yet the spirit is alive because of righteousness (because your inner spirit has already been redeemed and made righteous).
This is the specific reason you live by faith; in your own human strength, you cannot live righteously or do "good" works*. But, as Christ lives out His righteous life through you, you will live a life pleasing to God and complete the good works that God has prepared for you.
(*Note: Good works are those works that have eternal value; see Ephesians 2:10. Good works, as the Bible defines them, are always and without exception initiated by Jesus Christ who lives in you; they never originate from your mortal mind.)
Your life is now a life of faith. The Apostle Paul explains this when he said ...
Galatians 2:20 I have been crucified with Christ; and is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave himself for me.
To learn more about the essential elements of the Gospel: forgiveness, cleansing, righteousness, union and faith, Click Here.
To find out more why this definition of the Gospel is what the Bible really teaches, Click Here. (Note: This is detailed; but if you want to seriously examine the Biblical Gospel from the perspective of how the Apostles understood it and taught it, this might be of interest to you.)