Strugging with Forgiveness

I am struggling with forgiveness.  My fiancé left me to be with someone else.  I am hurt, angry, confused, and sadly, still in love with him.  I want to forgive him but forgiving him seems like I would be saying “what you did is ok”, and it’s NOT.  I know holding onto these negative feelings is only hurting me, but I don’t know HOW to let it go.  Please help me!