If you think that he or she was solely responsible because of what they did or didn't do, then you are missing the point. It's time to let go of that and focus on taking full responsibility for the choices that are available to you right now. Blaming others will only and always keep you stuck right where you are. It will take a new discipline to do this. You must understand that the pain you feel right now is only temporary.
Medical science has yet to prove that anyone has ever died from a broken heart.
Broken hearts can mend. It takes time and you must do the work. And you will do it when the desire to feel better about yourself again becomes stronger than the benefits of holding on to a past that obviously didn't work. It takes no strength to let go, only courage. Let the healing begin.