Speaking of personality traits, I seem to remember Dr. Cheney once commenting that he had not noticed a difference in the rate of Type A or Type B people developing ME/CFS, but did notice that Type A people were less willing to scale back once they started going further into the illness, something that often made things worse.
Stress...(which includes being too "driven") affects the immune system. Even Judy Mikovitz acknowledged that the XMRV retrovirus is "turned on" by stress...