A child's superstition - as old as the hills, at least North America's - says that a person should hold his breath while passing a graveyard. This may be to avoid inhaling, and being haunted by, the spirits of the dead; or people may do it for fear that their living breath will be stolen by the desperate dead.

Executives seem to do the same thing when passing through an economic crisis, and for similar reasons: They inhale, tighten their belts, and hope they make it to the end without turning blue and joining the dead themselves. Usually, that's a good enough response to recession: Lay off a few people, cut advertising, ice capex and R&D, and keep walking.

Not this time. This recession is too broad, deep, and long. You can't just wait it out. Cost alone won't cut it. When business comes back, it won't be to normal. Last week my colleagues at Booz & Company released a survey of more than 800 senior business leaders worldwide. Among other things, it showed that the majority believe that the recession will dramatically change the structure of their industry. In financial services, that number rises to 74%. (I wonder about the 26%.)  At the same time, more than half think their companies will come out stronger when an upturn turns up. If so, it won't be because of extraordinary  abilities of apneic oxygenation. It will be because they have simultaneously and aggressively reworked costs and rethought their strategy.

For entrepreneurs, this is a tricky moment. Disruption should be good for you, because  business-as-usual is good for the usual businesses. In normal times, market share changes about as fast as the front line did during the First World War. Booms and busts, however, rattle the status quo. In a boom, there's a new frontier-unclaimed market space, uncharted opportunity, and, usually, plenty of risk capital. Booms favor the new, the agile, the bold. Alexander Isosimov, the entrepreneurial leader of Russia's mobile phone company VimpelCom, published a great article in HBR called "Managing Hypergrowth" last April. It seems so long ago.

Busts crack the status quo in ways that are inherently less favorable to entrepreneurs. Customers are few. Capital is scarce and wary. But that doesn't mean it's time to look for a job. Busts create perfect opportunities-just different ones. To save money, big companies are eliminating marginal products, killing line extensions, cutting out SKUs-and, in the process, opening up space that can be profitable for someone who doesn't have big company overhead. They're putting a stop to new product introductions-including, perhaps, me-too products that were aimed at your niche in the market. They become more reluctant to try something new. They're freeing up assets you can get cheap and leaving customers in the lurch. The giant U.S. electronics retailer Circuit City is going out of business, closing nearly 600 stores, i.e. 600 leases, and abandoning about $11.7 billion in sales (last year) not all of which will be picked up by Best Buy. (They've also got a lot of store fixtures.)

For entrepreneurs, the difference between boom and bust is like that between country and city: Then, look for virgin territory; now, look for vacant lots.

Thomas A. Stewart is the Chief Marketing and Knowledge Officer of Booz & Company. Formerly the Editor and Managing Director of Harvard Business Review, he is the author of Intellectual Capital: The New Wealth of Organizations and The Wealth of Knowledge: Intellectual Capital and the 21st-Century Organization.