Let’s look at an example of what this would look like in real life. What causes your brain to assign a trauma to one event and not to another may become clearer.
One summer day you go to the beach with some friends, have a good, but uneventful day and really don’t think about that day again. In fact, ten years later you might not even be able to remember what beach you went to, exactly who you went with and even if it was a good beach day.
But what if you had gone to the beach with friends and you had almost drowned? Your memory might have a different outcome. Let’s say the lifeguard had pulled you out of the water after a rogue wave had pulled you away from your friends and sucked you under. You were told when the lifeguard brought you up on the beach, you were not breathing. He resuscitated you, you coughed up seawater and you came back to life, staring at all the people around you. That day at the beach you remember vividly. You remember whom you went with and which beach it was. You remember what you had for lunch and what the temperature was. You remember how your body felt as you thought you were going to die and how it felt when you came to. In addition to remembering the day clearly when something reminds you of that memory, a trigger, all the emotions you felt that day come pouring back. You might be reminded if you choke on a glass of water and the sudden terror of not being able to catch your breath might bring you back to the scene when you were underwater and couldn’t breath. Then all the other emotions and body sensations, as well as the whole event come flooding back. And the belief that you are not safe at that moment is there too. All the components of a trauma appear and you are back to that memorable day you almost died.
Now you can see why one event was so forgettable and you can’t forget the other one. Both were very similar to each other. Yet your reaction to the second description was very different. As was mentioned earlier, the traumatic event was sent to the reptilian brain at the base of the head. The reptilian brain only lives in the presence with no past or future. When this event gets triggered, that whole terrible event comes rushing back in the form of a flashback and you relive it as if it is happening now. The memory waits on the back burner for the brain to learn how to process it. Over time people have such a backlog of these unresolved traumas that one day all these trauma events become so overwhelming you can no longer use your coping skills to keep them on the back burner. Various trauma symptoms start to spill out and you seek professional help to guide you through your strong negative feelings.