Forgiveness is not foolishness. Forgiveness, at its core, is choosing to see your offender with different eyes. By the way, how can we grace-recipients do anything less? Dare we ask God for grace when we refuse to give it? This is a huge issue in Scripture. Jesus was tough on sinners who refused to forgive other sinners.
Remember his story in Matthew 18 about the servant freshly forgiven a debt of millions who refused to forgive a debt equal to a few dollars? He stirred the wrath of God: “You evil servant! I forgave you that tremendous debt. Shouldn’t you have mercy just as I had mercy on you?” In the final sum, we give grace because we’ve been given grace. And we’ve been given grace so we can freely give it. See your enemies as God’s child and revenge as God’s job.