The bogeyman is back.

Global markets are tanking on renewed fear that the United States will fall into a double-dip recession. All the major indices have gyrated between 3% and almost 5% in the red all day as investors sell just about anything that trades, from commodities to equities; the VIX, a measure of fear and volatility, is soaring as we test the lows set in August; and virtually no sector is safe today.

We Fools have said it before, and we'll say it again: Don't panic. If you have the urge to trade today, go bargain-shopping, like this Fool did during last month's drop.

The bad news
I'm not going to tell you it's all sunshine and unicorns out there, because it's not. Yesterday, the Federal Reserve released some rather ominous statements regarding the overall health of the economy and how it plans to do what it can. Here are some excerpts:

Information received since the Federal Open Market Committee met in August indicates that economic growth remains slow. Recent indicators point to continuing weakness in overall labor market conditions, and the unemployment rate remains elevated.

The Committee continues to expect some pickup in the pace of recovery over coming quarters but anticipates that the unemployment rate will decline only gradually toward levels that the Committee judges to be consistent with its dual mandate. Moreover, there are significant downside risks to the economic outlook, including strains in global financial markets.

The Committee intends to purchase, by the end of June 2012, $400 billion of Treasury securities with remaining maturities of 6 years to 30 years and to sell an equal amount of Treasury securities with remaining maturities of 3 years or less. This program should put downward pressure on longer-term interest rates and help make broader financial conditions more accommodative.

Source: Federal Open Market Committee press release.

The last section there details what investors are calling "Operation Twist," which the Fed hopes will drive down long-term rates to encourage lending but unfortunately may do little to ameliorate the jobs picture. This morning's jobless report showed a drop in initial claims, but it did little to quell the fears of a global slowdown since the overall level remains high.

Meanwhile, China's factory output fell for the third consecutive month, fueling the flames further. There is no doubt that the economy's not doing as well as we'd like, but that's still no reason to sell low.

Unsweet emotions
As a rule of thumb, any time you choose to invest your hard-earned dollars in inherently risky securities, you should have a time horizon of a minimum of three years, and preferably upwards of five. Investing is not for the faint of heart.

Part of being a successful investor involves distancing yourself from emotions that otherwise would prompt you to do irrational things. Right now that emotion is fear. We tend to love Warren Buffett around these parts, and it's not just because I share his birthday. By far, my favorite Buffett quote remains: "Be fearful when others are greedy, and greedy when others are fearful."

Judging by all the red coming across the tape right now, I think it's fair to say others are fearful.

You should view days like this as opportunities. Think back to March 2009, a month in history that presented opportunities that we probably won't see for another decade. No one knew the market was about to bottom, but if you were lucky enough or had the resolve to go out and start buying when everyone was selling, chances are you'd have a multibagger in your portfolio.

Today is not worse than it was at the pinnacle of the financial crisis.

Next steps
Move away from the monitor. Turn off the TV. Go outside and take a walk. Play with your kids. Remember that the future is far more important to investing than is the present or the past. At the very least, if you choose to ignore my advice and remain glued to your screen, be greedy.