Baseball Bat to the Knees and the Evolutionary Intention of Emotional Pain

I don't always relive bad memories, but when I do... I fuck that shit up

So, I had this dream of person from my past that was an evil little bastard, and it took me out at the knees.

The impact of the fresh memory was nearly unbearable and has left me a bit of a wreck of vulnerability. I feel gun shy to anything outside of my house, the world at large seems too chancy. 

I don't like that. At all. 

It will take time for those memories to wear down again and for me to regain my regular scheduled programming;  I get that, but I don't like it.

I like to feel what is real today. My real life today. 

But it got me wondering, why do memories feel so painful. So deeply and utterly painful? Outside of the obvious I'm an adult now and can fully appreciate the wrong that was done kinda thing, why can I not still be a little bit more objective about it, why do I feel the pain so acutely?

And the big question, is there value to feeling that pain? If yes, what is it?

I believe we are given what we need to survive (reflexes, responses, memory storage to build patterns of responses etc) and giving the body/brain the benefit of the doubt - this acute re-experience of a trauma/memory emotion must have value. 

Without knowing this value and being subject to our environmental/societal influences, I believe that a lot of us could succumb to the pain and fear responses and not evolve - as would be the intent of the evolution process. 

So, is the bonus factor of having experienced trauma empathy? Is the reason for the physical pain to restore and maintain a worldly empathy so that we can go forth and do better?

Brain: this shit happened and we're going to store it as a trigger or warning so that we can flee or fight the same set of circumstances should they arise again - the basic reason for storing "bad" memories. But why connect the pain to it? Surely the brain can just pass the fight or flight response without reliving the pain. 

Brain: we are also going to allow you absolute, devastating compassion towards your role in this memory. 

Why? I want the science, the numbers, the data. 

Did the brain just fuck up during programming, was it rushed or simply thoughtless? If {bad memory} then {store}

can (and should) we add, if {bad memory} relived >  !=include {emotional response}

I mean, that's my atrocious attempt at php in human programming - but that's besides the point.

What would we lose if we didn't also relive the emotional response to the memory (should it be triggered)?

I think it's needed, so although I don't like, I will walk beside the pain and honour it - but I'll do it like a science fair project. I don't want to get attached to or identify with the pain. 

Hi, welcome to my science fair project for triggered bad memories. Here, we see the memory that was triggered and here we see why with the "fight or flight" response. But over here we see interesting additive companion results of fear and pain. 

(And we see two unhappy minion like characters bouncing about and yammering gibberish, both vying for attention but cowering at it at the same time. )

These two factors don't appear to have a clear role in the "bad memory = flight or flight" process. Are they to the memory what the appendix is to the body? Or are they required to obtain optimal compassion - a key factor in our hopeful evolution?

I'm tired now.