If you have had an extremely frightening experience, you may be carrying the reaction to that experience around with you. It makes sense that the reactions to traumatic experiences become part of our ongoing reaction repertoire. This is a survival adaptation. However, this new reaction repertoire often includes maladaptive reactions such as being overly on the lookout for danger, experiencing flashbacks of the incident or incidents, recurrent nightmares, or feeling undue guilt or responsibility.
Inviting our thoughts and feelings into awareness allows us to learn from them rather than be driven by them.
These reactions, that may have been helpful at some point, now serve to cause panic and paralysis in a triggering situation. Triggers are those parts of a current experience that remind us of the previous traumatic experience. For some it is not conscious, so panic and terror arise as a bodily sensation beyond awareness. Dr. Stephen Porges calls this neuroception.