I think it was Dave Chappell who talked about being paid $10,000 in cash after a show and then had to take it home and how paranoid about everyone he was.
He compared that to walking around with a vagina. He walked home with $10k in his bag, that no one knew about, but it would only take anyone of those people he walked passed to be a wrong'un for him to be screwed.
Then imagine having to walk around every day with $10k in your bag, with a sign on your bag that says "cash in bag".
The perception of risk is obviously a personal one, but the effect of a perceived risk as a constant is going to be far more debilitating than the risk of a one off.
Someone mentioned lightening. If you live in the UK, it won't rain every day, most of those rain clouds won't be thunderous and you are likely to be near taller objects that will attract the lightening first. So you don't think about getting hit by lightening. If, however you live in a place where there are thunderstorms everyday and you live on a flat plain, the worry of going out is far greater, you'd think about it every single day.