Boiling ACIM down to pure logic, we end up with this.
"Only the truth is true and nothing else is true."
) God's realm and creation are TRUE.
2) The world we made in dreaming is FALSE.
3) Forgiveness means becoming TRUE while inside of the FALSE in preparation for moving into the realm of the TRUE.
4) Eventually returning to the actual TRUE realm.
So forgiveness really just means aligning yourself with the true nature that you have IN heaven, while you're temporarily seeming to be outside of it. Becoming as heaven-like and aligned with reality as possible. As identified with Christ Spirit as possible. As under ONLY God's laws as much as possible. As expressive of God's loving nature as possible. All the while being still in this dream world which seems like imagined hell and death, SEEING from and with Truth, a perspective which opposes and invalidates the FALSE world.
And we take the Holy Spirit's hand who SYMBOLIZES the truth and we attempt to become in alignment with that symbolism, even at the body level symbolizing eternal life, so that we are as close to heaven as possible and ready for God to take us home.
You can also describe it this way.
1) The PREMISE of the Kingdom is God, immortal truth. The logical outcome of that premise is the creation/extension of eternal life as the Sonship etc.
2) The ego's idea of separation is a FALSE PREMISE, resulting in an entire seeming world which is entirely FALSE. It is opposite the Kingdom in every way.
3) Having made the false world and having CONFUSED IT with the truth, it is given all of truth's properties such as "reality" and "existence". It now seems to be real and exists. And now we experience the nightmare of hell.
4) Forgiveness ONLY means, bringing the PREMISE OF THE WORLD into question, and switching from the ego premise to God's premise. That is all. Nothing else.
5) To question the world's reality, to strip it of truth, to disbelieve it, to side "against" it, to deny it, to recognize it is FALSE and not true, to sort out how and why it is unlike God, and to realize it is NOTHING because an opposite to God cannot exist, IS FORGIVENESS.
We simply need to shift from the entire spectrum of ego reactions of "its a real world and bad things are really happening", to "the world is NOT REAL, it's a dream, and it is NOT happening." That is changing the premise of the separation. That is the only logical thing you can do and it's all that's needed.
When what seemed like real war, real attack, real suffering, real death, are put into a context of ITS A DREAM, not a reality, it completely reframes everything in a different context, and the ENTIRE THING is uprooted and stripped of its threats and dangers and sins. It has no further power to affect you because you recognize it is FALSE and unreal, NOT a real world, and NOT really happening. And be glad it is so.
"There is no death, the Son of God is free."
"There is no world."