When it ( your brain) perceives that you are either safe enough or strong enough (or both), the walls it created between you and the trauma breaks down and with it the increase in symptoms.
Yes, I believe this too. My H and I had moved 14 times in 16 years including going half way around the world to care for my mother-in-law. When we came back to the USA, we moved from the suburbs into New York City. I am not a city girl but needed to finish college. Last move was to here 20 years ago.
I remember one Febuary when my very safe pastor came over for tea. The baby was asleep in my arms. A lovely, peaceful and tender moment that was. We were sitting looking out at fresh sparkly snow and I felt like at any moment a molotov cocktail could be thrown into the livingroom , explode and kill all of us. The two pictures did not match. I have since learned that is called hypervigilance. It made sense when we lived in cities. It made sense when we lived on the edge of the biggest slum in NYC.
It did not make sense when I was safe. I had a roof over my head, no worries about enough food or anything else. I had had a few odd moments growing up like when my roomate's first year girl came up silently and stood behind me in our narrow hall. I turned, screamed, and went into a full fetal tuck. Moments later, I was up and sorry for having embarrassed the new girl. She was tall, like my mother. She had blonde curly hair, just like my mother. I think I could get up so fast was because I snapped into disassociation quickly.
Once in India, my H and I were driving on a dusty road straight west as the sun was setting, huge and orange as seen through the dusty atmosphere. Some safe little girl part of me pipped up with delight, "Looky,looky a full sun." Clearly, she only experienced life at night. She knew the moon had phases so assumed the sun did too. I was embarrassed but H thought I was just gooofing around.
Incidents like this with no memory of trauma were discordant with reality. I finally went to group art therapy sessions to start with. I trusted what came out of me to be clear of any therapist's agenda. 20 years ago...some success.
This one may make you laugh. We can hear bang type noises all year round. I lived here for 10 to 12 years thinking that there was a manufacturated home industry nearby and what I was hearing was a nailing gun for roofers. As therapy went along and more of the traumas came out. The sound became so far from neutral. An important family moved in a few towns away. There were two police shooting practice ranges and a detail bodyguards as well as a private shooting club. One day in a full blown panic attack, I figured the sound out, gun fire. That is a very big trigger still.
I think you are right, we can only begin to do trauma work when we are safe.