all or nothing thinking error anxiety behavioral experiments biased information processing bodily sensations body noise catastrophize cognitive behavioral therapy cognitive restructuring confirmation bias coping mechanisms core beliefs cycle of health anxiety death anxiety emotional reasoning thinking error examine the evidence excessive checking exposure fear of death fear of disease fear of dying process fear of unknown health anxiety hypochondria intolerance of uncertainty memory bias overestimating threat preventive behaviors reassurance-seeking safety behaviors socratic dialogue symptoms thanatophobia thinking errors threat bias underestimating coping