I don't have a clue for this one, but we all know the phrase time heals everything.
Maybe look at things exactly the way they are, so you know exactly what it is you're going through.
Understanding what the circumstances are might help you to slowly let it go. By slowly it can mean years. Forgive yourself, forgive the other person and forgive life for being an asshole. Also remind yourself that just one other person cannot have power enough to kill you, your heart may be battered, but there's still a tomorrow.