Can I forgive and forget?

They say humans should always learn to forgive and forget. That is always a virtue.But what if one cant?What if one feels that some mistakes are beyond forgiveness?Are there mistakes that are beyond forgiveness?Or is it just that we ,mortals ,dont just have the ability to forgive someone who hurt you .Or even if not forgive,atleast forget.I can forget mistakes by others easily,but are we sure we can forgive? And mortals would always think one fundamental question."Why should I forgive if it was the other person who hurt you" ans ordinarily a person would think..Why forgive?The question still remains unanswered . Should one forgive other humans even if they feel their mistakes is beyond forgiveness?