He's right, you know.
If you continue to hate your former enemies, they will never become your friends and allies. Over the centuries, we have seen former hated enemy states eventually become trusted allies. It's just a matter of allowing the past to remain in the past. President Obama is, by his actions, allowing his former opponents to join him in dealing with the problems that face all of us. It's not just a case of forgiveness – it's all about positive thinking and practicality. You can't continue to let the past determine your future. You need to forgive and forget and look forward.
In our own private lives, we need to carry this same positive attitude forward. Don't dwell of what might have been – look to what might yet be.