Why is it so difficult to forgive?

I spent over 2 years with the sketch of this painting ready.

Maybe I didn't have the courage to start doing it because of the powerful message it carries within it, maybe I needed to learn what I wanted to convey before bringing it to life.

Thanks to all the people who were part of this collective construction and answered my question: Why is it so difficult to forgive? Because all those messages out there are not only my perspective, they're yours too.