Today the stock market is getting slammed, with the Dow down over 360 points. In my view, that's because many of the bad things that investors have been worrying about for years are all happening at the same time:

• Spiking oil prices -- a barrel of crude oil was up $1.12 at $77.
• Tanking housing market. Disappointing results from home builders including Pulte Homes Inc. (NYSE: PHM) and D.R. Horton Inc. (NYSE: DHI) -- squeezed by a sluggish environment from home sales and continued defaults in subprime loans -- weighed heavily on the market.
• Drying up of private equity financing -- as I posted earlier today.

Over the last few weeks, these worries have been masked by an onslaught of big mergers. But the mergers aren't happening today. Moreover, if the credit markets decide to turn their back on future deals, the only thing to stop the market from freefalling would be big companies exceeding earnings expectations.

What should you do? Probably nothing if you're in it for the long term, eventually all the bad news will come out and there will be a buying opportunity. But not yet.

Peter Cohan is president of Peter S. Cohan & Associates. He also teaches management at Babson College and edits The Cohan Letter. He has no financial interest in the securities mentioned in this post.