Just over a week ago, the stock markets had a rough day overall. It turned out to be no big deal as some of the losses were regained by the end of the day and most of the losses were regained the next day. Still, it was headline news and many people became scared of a bigger economic loss. Why did one bad day have such an impact? In this discussion, BankRate.com's Greg McBride explains what happened and what we should learn from it when it comes to our own saving and investing.