If the "stressors" get you, learn about adrenal fatigue ( mild insufficiency).
These people can be fine unless they go through a stressful period. Their weak adrenals can't keep up with need for stress and other steroid hormones.
Getting adrenal support has been hugely helpful for a close friend who suffered for decades with PSTD and adrenal fatigue. Today I can't imagine she'd be diagnosed with PTSD.