From personal experience, my feeling is the PTSD is caused how you deal with a stressful item (no matter the cause), bottle it up (we all do) and you have a problem, let the emotions flow (hard to do) when need and the PTSD solves it self (more or less) as there is no pressure build up to let it out of control.
Sounds very simple put this way, but even from personal experience it is way more complicated than that as letting the correct emotions flow when needed just isn't that simple.
All I can say from what I've experienced:
Bottling it up doesn't work (this definitely leads to a problem at some point),
You will need to have an emotional out burst (hopefully in a safe place to do it with support),
Time does heal, let it (at the least it dims the memory),
Don't deal with alone, friend, family, specialist, or stranger may be the sound board you need (remember safe place)