Why Forgive?

I've just began reading a book called 'why forgive'. I figure, what do I really have to lose? I've lost everything, at some point, I must lay down my arms and regroup. Restore the infrastructure of my souls queendom.
The hard part is what do you do when someone doesn't want yout forgiveness? When they feel absolutely justified in everything they have ever done? What then? How do I digest that? How do I not allow it to permeate my inner most thoughts, as to not disturb the newly aquired peace?  I'm hoping that one day when I sort through all of it, I will gain the answers to these questions.
Although, I notice that as I am forgiving, i am becoming physically lighter. It sounds silly but its real. My body feels like a layer is being peeled off, in a refreshing sort of way.  Its different. I like it. And I'm hoping that when I finally get to the core, I become so light that I float.
J§