I recently received a message from a listener that asked if they really need to forgive someone who does the same harm to them over and over.  Yes, but that does not mean forgive and forget.  That is not what the Lord is telling us in Matthew 18:21-22.  Extend the same mercy that Christ has given us.  Extending mercy is good for us as well, but that does not mean that don't use reason and protect ourselves in the future.