If you have a forgiving attitude it means you overlook errors because you do not make them and recognize they do not exist. You are forgiving because by looking with forgiveness you shine a kind and gentle light on all that you see, acknowledging its innocence and yours.
It's when you fail to be forgiving that you enter into making illusions, perceiving guilt, and are calling for punishment.
God's attitude is that you are always innocent. Holy Spirit's attitude is the same. Holy Spirit is always forgiving. If there is anything you think you've done wrong, it is forgivable. Forgiveness extends from unconditional love and recognizes you have not really done anything at all. That is why forgiveness is a key part of the atonement principle - there is nothing to forgive because nothing has happened.
When we do fail to be forgiving, we enter into a state of judgement in an attempt to explain why we are not forgiving. If I can judge another and condemn them, this is my attempt to explain that I did not forgive because clearly the other person is in error and this calls for me to righteously judge them.
"He who would not forgive must judge to justify his failure to forgive." - ACIM
What I need to then do is stop and recognize that I am not being forgiving, and that I need to get back to a forgiving, overlooking attitude, which recognizes innocence and acknowledges the atonement. This doesn't necessarily refer to the `process` that we seem to go through to get TO a forgiving state of mind. When we're in the forgiving state of mind - Holy Spirit - all is forgiven already. But if I'm in a state of condemnation, I need help to get my mind to stop this and to resume forgiveness.
We call it forgiveness when we undo these illusions and when we work on correction of thought and adjustment of perception. But such corrections are only there for the sake of getting mind back to a state of constant pure permanent forgiveness. Forgiveness isn't therefore something you 'do' its a way of being in love. The curriculum of returning to a forgiving attitude is just that, an illusory path of corrections of the mistakes that we're making in our forgiveness.
Some call it practice - to practice forgiveness, in order to learn what forgiveness really is. Or moreso, to unlearn what forgiveness is not. But it isn't practice that produces forgiveness - the light of truth is already established by God and it is His unconditional love that is constantly forgiving through us. We share in that. Our so called 'application' of ACIM principles is more to do with undoing the ways in which we have failed at forgiveness, removing blocks to the awareness that all is forgiven already, so that we can be restored to a constant state of pure forgiving.
Once we reach that complete awareness of forgiveness, and join with Holy Spirit fully, we will cease to make errors such as judgements and will recognize there is nothing left 'to forgive' because forgiveness is complete. And this forgiveness is a protection because it pro-actively fore-gives in order not to enter into error of judgement. So long as you stick with Holy Spirit and see as He sees, you're good to go.
All is forgiven because nothing has happened to assail the Kingdom of God and nothing ever will. This is good news.