The stock market has declined substantially, but there has never been a better time to invest. Many people tend to buy when the stock market is red hot and sell when blood is on the streets, which goes against the "buy low, sell high" mentality that every great investor should embrace. The news has portrayed this as the worst meltdown in the stock market and economy ever, but in reality this sort of thing happens every decade or so. Long-term Capital Management nearly caused the collapse of the stock market in the 90s, for example. The key is just riding out the bumps and focusing on the long-term - whether it be in US stock markets or abroad.

From CNN Money:
The market is now down about 10 percent for the year and more than 15 percent from its high in October of last year. Sensationalistic headlines read something like "worst start ever for the stock market," and "as January goes, so goes the year." Such anxiety-inducing hype makes it virtually impossible for us to ignore the doom and gloom and just stay the course, but that's exactly what you should do.