I used to get horrible stomach pains every week like clockwork due to a weekly church youth group meeting my parents forced me to attend. I don't recall why this thing upset me so, but I certainly remember the agony in my guts, so something must have been wrong.
More recently, I suffered an attack of shingles (according to Dr. Google), which is a recurrence of the chickenpox virus (from around forty years ago) triggered by stress, in this case courtesy of my evil, demented landlords. They sent workmen into my apartment, which freaks me out more than just about anything else, and it took them three weeks to do a job which should only have taken a couple of days. It hurt like hell, and has left me permanently scarred, though fortunately only on the back of my head and neck where it doesn't show too badly.