A traumatic event is much more than just a story that happened long ago. The emotions and sensations which were experienced at that time may have become imprinted during the trauma and instead of being memories they are still experienced as disruptive physical reactions and sensations in the present. And often these may become worse, not better, with time.
The human brain detects threats via the limbic system, which has the job of keeping you safe and usually happens completely subconsciously. It is responsible for the tagging of negative experiences with an emotional charge designed to indicate that something is wrong. Each time there is, for example, a traumatic experience where a person felt powerless, the limbic system tags this as unsafe and stores it in its memory bank. It is continually scanning the present environment, comparing what is happening now with its stores of previously tagged memories and if it sees a connection with a previously tagged memory it instantly puts your system on high alert and a fear response, either fight, flight, freeze or fawn, kicks in.
In his book "In the Realm of Hungry Ghosts" Gabor Mate writes, "The greatest damage done by neglect, trauma or emotional loss is not the immediate pain they inflict but the long-term distortions they induce in the way a developing child will continue to interpret the world and her situation in it. All too often these ill-conditioned implicit beliefs become self-fulfilling prophecies in our lives. We create meanings from our unconscious interpretation of early events, and then we forge our present experiences from the meaning we've created. Unwittingly, we write the story of our future from narratives based on the past... While Gabor is writing about a child's trauma, this may also be the experience of a person experiencing trauma at any age.
At the very core of recovery or change is self-awareness. Those who have been traumatised frequently experience various levels of physical sensations and reactions such as tightness in their chest, churning in their stomach, tremors, nightmares, flashbacks, etc, from mild to intolerably uncomfortable and avoiding or denying these sensations most often increases the risk of being overwhelmed by them. However, those who are traumatised are often fearful of feeling. The traumatic event may be months or years in the past but now their emotional (unconscious) brain keeps generating bodily sensations which keep them fearful, anxious and helpless. This causes the sufferer to to do their best to keep their body frozen and their mind shut to try and avoid feeling these extremely uncomfortable emotions or sensations.
Because their sensory world feels so uncomfortable, trauma survivors may avoid situations that trigger them such as certain social activities or making love. Many also become compulsive eaters, drinkers or addicted to drugs in an attempt to avoid these feelings.
EFT (tapping) has various gentle techniques which allow the trauma sufferer to safely, gently and slowly release these disruptive physical reactions, sensations and emotions so the memory remains without any charge.
While it may be safe to work on oneself for a "small" trauma, the best results may come from working with a trained Clinical EFT (tapping) Practitioner. And it is always safer to work with a trained Practitioner for a larger trauma.
References: Book - The body Keeps the Score, Bessel Van Der Kolk