Dow Jones declined 174 points on worries over telecommunications restrictions on Chinese companies selling within the U.S. The stock market is like a roller coaster when small changes in strategies lead to bumps and burps in the market. The overall trends often stay the same but the day changes are what put many executives on the edge of their seats.
If I was an investor, assuming I had money like some do, I wouldn't worry about day bumps. My concern would be more about long-term trends in the market. If industries are changing and some companies are being pushed out that would make me concerned.
It would also be important to see what the companies plans and trends are. If they don't have a solid plan to introduce new products and services that will improve their financial performance they are likely to suffer in the long run.
Equally beneficial is to not put all your money into one place. You want to hedge with industries in different sectors. Especially those that are known to work independently of each other. Some may decline while others rise creating security.