" When we feel safe, the parasympathetic nervous system brings about rest and relaxation. However, when we feel threatened, the parasympathetic nervous system can go into a defensive mode associated with trauma, known as a “faint response,” which includes feelings of helplessness, fatigue, and eventual collapse. When a child spends an extended period of time in a faint response, these feelings of heaviness, sluggishness, and tiredness persist into adulthood and can influence their overall sense of self. "

― Arielle Schwartz , A Practical Guide to Complex PTSD: Compassionate Strategies to Begin Healing from Childhood Trauma