Stress AND/OR an injury to your nerves can cause a shingles outbreak..
Yes, I've been there too.. Had pox as a kid, and my outbreak was directly related to a barber, who decided he needed to hurry up my haircut, and smacked me on my radial optic nerve with his clipper. (Eyebrow area)
Full blown shingles in 12 hours..
Painful yet livable.. Crackerjack drugs..