The Bible has a great deal to say about forgiveness. The world, and even many in evangelicalism, justify their anger. As MacArthur notes, anger is fueled by psychology and narcissistic self-centeredness. Our churches today are now even telling their members that in order to extend forgiveness to others that true believers have to forgive themselves.
Further, preachers intone that it is a necessity to forgive yourself for your own sin or shortcomings. This is a dangerous teaching that quickly borders on heresy for it leads to the teaching that we have to forgive God.
Forgiveness is necessary in order for true believers to portray the Christ by which we are named. He forgave us when we were unloveable and did not deserve to be forgiven. To NOT forgive is to make ourselves to better than Christ.