Forgiving would be a good thing. Because one you don't want to carry all that hurt, it will just weigh you down and nothing else. Two, if the person really matters and you can't just let go of them then you have to forgive. Yes cry, yell even throw things at them if you want But forgive.
If the mistake is something unforgivable, even then forgive them and chuck them out of your life because if they did something unforgivable they are not worth your friendship. Ignorance will just hurt you and you 'll get nowhere. Hope that is helpful :)