Vanguard has done some interesting work.  They looked at the stock market for every single day from 1990 until 2015.  During that 25-year period, they identified the 20 best days and the 20 worst days.  What they learned is that these 40 different days, both up and down, tended to be clustered around geopolitical events and within a month of each other.  Take a look at this chart:

There is a real lesson in this.  If you over-react to geopolitical events and sell, you are very likely to miss the major up day in the near future, usually within a month!

The only caveat I would add is that I would not sell if Russia invaded another country for example or China shot down one of our planes, but I would sell, notwithstanding this research by Vanguard, if the Bank of England shut down for example or the Shanghai market collapsed.

Fear not geopolitical surprises.  Fear not normal recessions.  Fear only financial collapse!