writing and editing the writing afterwords helps me to get a better understanding of the events. I took some journalism in college, I try to apply the same standards my professors would have used to grade my scrawlings about my traumatic events. For me, being concise and trying to apply the who, what , where, when guidelines helps me get to the why, somehow.
If just writing to yourself helps then why stop? Some people (me included) get a lot out of drawing, painting, singing, all sorts of other ways to get the feelings out without having any other goals beyond the purge and that's definitely a part of it all that works for a lot of people like us.
When writing it out I try to be as expository as possible, I try to make it read like a very short and factual, clear and understandable brief on the subject. There are a lot of thoughts that don't get to the final draft, but somehow deciding what to leave in and what to leave out makes me look at the real core ideas quite a bit harder and that's my goal in writing it down in the first place.
I think in ideas without words attached to the feelings, I tell the story as my brain sorts out the vocabulary to use, I write with the intent to sort those words to make it all as clear and applicable to the feelings that started the whole process as possible.
This all takes practice, and trying lots of approaches to find the stuff that works is the first step for anyone. Keep trying, it is the only thing that you can do if you want to get better at it.