You might wanna look up terms hypervigilance and hyperarousal in relation to PTSD. I get hypervigilant and generally can relate to that feeling of being 'on guard' and needing to expand my awareness for cues 'just in case', so that I can be ready before things start going wrong. When I am feeling poorer this can get to a level of bordering on suspiciousness and anticipating the worst in everything, misreading people quickly and anticipating negativity where there is none (or where positive stuff is lacking). Very draining and very hard to stop even when I feel sick of it.