Forgiveness is a big subject, and it shouldn't be taken too casually. We are told to forgive others. We are told that Christ died for the sins of the world saying, "Father forgive them, for they know not what they do."
And yet, we also read in the Bible where David calls down curses upon his enemies. We are told that God hates His enemies. Where do we draw the line, and how do we resolve this apparent contradiction?
It, quite simply, is that God is willing to forgive anything, assuming people are willing to come home to their original calling to live in the image of God. All sins can be forgiven, and Jesus' blood covers the sins of those who are willing to repent in his name, returning to live as servants of God.
We think that bitterness in our lives, due to how some have treated us in the past, is something we need to just dismiss from our lives. But God recognized in the Passover meal that bitterness is an essential aspect of our lives in this present age. We will suffer in a variety of ways. Life is no picnic.
So even though we may be willing to forgive, some who abuse us simply are not going to be forgiven by God, because they remain hostile to God and in rebellion against God. And we shouldn't forgive them either--not if God has devoted to destruction those who are His unrelenting enemies.
Much of this requires maturity and experience, along with the ability to let God speak to us. If we insist on making our own judgments we won't be able to hear God's judgments. How important it is that we stay under the cross, and let God decide all matters!