It would seem that the thing that hurts the most is the rejection thing, like we weren't good enough to keep the relationship going or weren't deserving of a respectable good bye. Of course that self-inflicted negative belief can be a self-defeating action, if we choose to dwell upon it. We need to do some self examination and critiquing, but, bottomline, some relationships don't work due to incompatability.
Some take the tact of calling the other person a bad name and blaming them. Daniel Gilbert, in his book, Stumbling On Happiness says that we feel better if we have someone to blame for our pain. Blaming someone else for our pain is not bad, if we only do it for a short time as part of the greiving process. To conclude with blame is a consciously and emotionally stagnating process. We have to move on and rise above the situation. If it wasn't meant to be, then it wasn't meant to be.
There is a certain philosophy that says, in loosing, you're actually gaining: gaining a chance to be a person you wouldn't otherwise be.
"Something is important because we give it importance" are words my friend Bill, who is also a Therapist, gave to me years ago. Meditate on that: Anything that is important to us is so only because we make it so. We are the ones responsible for giving credence to chosen entities, relationships, material things, or even beliefs.
There are many schools of thought that prescribe to the loosing-is-gaining concept- from Zen Buddism to Judeo Christianity.
I pray adamantly for apathy toward the things that are more liabilities than assets in my life. To be able to have a lack of feelings toward those entites, relationships, material things, or beliefs that are unnecessary and spiritually downing. It takes a lot of continual examination, understanding, and energy, but then end result is a certain peacefulness that pocessing can't provide.
Here's hoping that you find understanding and peace in your loss, A&OXNone.