We sometimes can not imagine forgiving someone for the pain they have caused us, but the more we think about it, the more it pains us, and we can not let go. Even when we do let go, if the name of that person arises it forms bitterness in our hearts, if we cross paths with that person in coincidence, it aches and breaks our thoughts and feelings into rot. So why should we forgive someone or something for being so painful to us? Would you forgive it if you knew that, it really is the only solution to your pain?
Forgiveness really is the cure, it is your only medicine, and there is a reason for that. A cut will only burn you until it heals, and it heals because your body forgives you for the cut. For putting yourself in places where it can hurt itself. We learn by experiencing, by going through with the pain. But not wanting to forgive is self harshness. Because you are the only one capable to forgive yourself first, and then forgiving the cause.
وَمَا خَلَقْنَا السَّمَاوَاتِ وَالْأَرْضَ وَمَا بَيْنَهُمَا إِلَّا بِالْحَقِّ ۗ وَإِنَّ السَّاعَةَ لَآتِيَةٌ ۖ فَاصْفَحِ الصَّفْحَ الْجَمِيلَ [Al-Hijr : 85] And We have not created the heavens and earth and that between them except in truth. And indeed, the Hour is coming; so forgive with gracious forgiveness.
Where do I put my faith? Do I put my faith in something loveless that someone did to me, or in the eternal love that lies beyond & corrects all things? To the extent that I withdraw my attachment to what you did, I will no longer be affected by what you did. I have decided to put my faith elsewhere. That is the miracle of forgiveness. [from my readings of: A year of miracles]