Stop, just stop. To steal a line from Cameron Crowe's 1989 movie Say Anything: "You must chill. You must chill."

Yes, I realize that the market's imploding -- I get it. Since May 3, the Dow Jones Industrial index has lost nearly 5% of its value. While up one day and down the next, the net effect is that Boeing (NYSE: BA) has crashed 5%, Cisco (Nasdaq: CSCO) suffered a 9% short circuit, and Bank of America's (NYSE: BAC) cash register is nearly 10% short. Heck, one of my own stocks, Barnes & Noble (NYSE: BKS), suffered worse than any of these, losing 14% of its market cap since the beginning of May.

Sure, stock-specific news drove part of those declines. Cisco posted strong profits, but its revenue forecast was considered relatively unimpressive. The crisis in Greece has investors worrying about B of A's exposure to the continent, although a $1 trillion EU/IMF government bailout will go a long way to covering that up.

But bad news doesn't explain everything. Boeing's announcement that its 787 Dreamliner is on track for delivery this year is undeniably good news. And as for my own beloved Barnes & Noble, Google's plan to sell digital books was hardly unexpected, and doesn't change the fact that Barnes &Noble is a cash-producing machine, selling cheap.

Regardless, we've just seen nearly three months' worth of gains wiped out in a matter of days. Scary.

Yet if you're reading this, it means I'm still typing. I haven't jumped out any windows. (Not that it would help matters any, as I'm on the ground floor.) That sort of dramatic overreaction doesn't help. Panicking as your stocks plummet won't slow their fall, and it won't salvage your portfolio -- it'll just lock in your losses.

Well, what should we do?
You should thank the market gods (or your deity of choice) for days like May 6, which provided an object lesson in the volatility of the markets. Maybe it was the crisis in Greece that caused the "flash crash." Or the Goldman fiasco. Or perhaps it's true that, as news reports suggest, a few accidental sell orders on Procter & Gamble (NYSE: PG)  and 3M (NYSE: MMM) shares placed by Wall Street's mysterious "black box" software programs were the real catalyst for the sell-off. We're still not completely sure.

Whatever the reason for the market's sudden bout of volatility, it does at least remind us that asset prices can go down as well as up. Otherwise, we might do something stupid, like, say, pay more than 120 times trailing earnings -- and almost 50 times forward earnings -- for a share of Wynn Resorts (Nasdaq: WYNN). Or buy a $200,000 house for $300,000, finance it with a no-money-down subprime ARM at 2% with a six-month balloon payment, and then wonder why we can't afford the mortgage when the rate resets to 6% and our monthly payments suddenly triple.

Hypothetically speaking, and present company excluded, of course.

No, no … what should we do about the stock market?
Oh, right. Well, just keep on doing what you've been doing. I did say "present company excluded," right? So keep collecting and depositing your paychecks. Keep researching high-quality, low-priced stocks. Keep buying shares at a significant margin of safety. And, as always, keep purchasing no more of any given stock than you can afford to lose, because we all make mistakes from time to time.

Once you've got that down, though, it's time to get greedy.

Greed is good
A lot of investors are saying things like, "Oh, spit! OMG! The sky is falling!" right now. Even the pros are panicking. The hedge fund types? They're worrying about making their quarterly numbers, and they're selling out of positions they love, in a frantic attempt to stanch the bleeding.

Meanwhile, you should consult your stock "wish list" and see whether the panic selling has pushed any of your favorite stocks down below your hoped-for buy-in price. You've got a wish list drawn up, don't you? Today just might be your lucky day.

In short, while the so-called Wall Street Wise are busy selling their dream stocks, you should be marshalling your pennies, updating your buy list, and deciding how far ExxonMobil and Pfizer have to fall before you'll be willing to buy in.

Further fearless Foolishness:

3M and Pfizer are Motley Fool Inside Value picks, while Procter & Gamble is a Motley Fool Income Investor choice and a Fool holding. Fool contributor Rich Smith owns shares of Barnes & Noble. The Motley Fool has a disclosure policy.