So long, May -- you won't be missed! Rarely has "sell in May and go away" seemed so prescient. The Dow Jones Industrial Average (INDEX: ^DJI) is down 6% with just a couple of hours to go before the month closes out. May has scuttled nearly all the momentum from a record first quarter when the Dow saw its best returns since 1998. The index now sits up just 1.7% on the year.

In today's action, at 1:45 p.m. EDT the Dow sits down 0.09% while the Nasdaq (INDEX: ^IXIC) is seeing a steeper 0.58% plunge.

Why the week turned
A Molotov cocktail of global concerns and a poor U.S. economic data has dampened optimism that had surfaced on Tuesday. On that day, positive housing news and hopes of a China stimulus started the week out with a nice gain. However, at the time I warned that hopes of a large Chinese stimulus went against quotes from China's official news agency.

As the week wore on and it grew clearer that China would be holding off on another large stimulus, the same companies that saw Tuesday's pops faded. Caterpillar (NYSE: CAT), which relies on continuing high infrastructure spending in China, is the Dow's biggest laggard today. The company is down 2.52%, posting a significantly larger loss than any other component.

China knows that a knee-jerk reaction like a massive stimulus would only worsen its long-term predicament of too much spending on investment projects. That stimulus in turn would also pile more debt on regional governments.

Looking ahead
However, while China's slowing growth is one sideshow to this month's falling markets, the main event has been Europe. A Spanish debt downgrade led to losses yesterday. Today, there are reports that the IMF is discussing how to handle a bailout of Spain's Bankia if the country is unable to save the bank.

It's an ever-changing situation, and periods of despair and hope flow seamlessly from hour to hour. For example, the market's rebound after a sharply negative first hour today was attributed to new public opinion polls that showed a pro-bailout party was leading opinion polls in Greece ahead of its June 17 elections.

Yet, it's also worth noting that the lead is by a slim 1.7 percentage points. From a sample of 1,128, that's within the margin of error. Also, that lead can be tenuous with parties jockeying for different coalitions within the new government. In short, whether or not Greece elects a pro-bailout government is far from settled. The unfortunate reality is that means continuing rockiness in the weeks ahead.

To the bomb shelters!
So we end a May that was trying, to say the least, but lots of the same instability remains in the month ahead. If volatility is a ride you're not best suited to handle, a good bet is to stick with high-quality Dow blue chips like McDonald's (NYSE: MCD) or Coca-Cola (NYSE: KO). They'll drop with the market as well, but as high-quality names with a lower beta, their fall will likely be less steep. They also might not run as much in a rebound, but have proven to be long-term outperformers all the same.

Take the long-term view
That's it for this market checkup. While staring at stock screens all day can be bad for your health, the best investors don't pull out of the market. Instead, they find stocks they can live with for the long haul. Check out The Motley Fool's special report on long-term investing, where you'll find three promising stock picks for long-term investors, along with some tips on how to invest for your golden years. It's free, but don't wait -- get your report today while it's still available.