As the poet Robert Burns put it, “The best laid schemes o’ Mice an’ Men / Gang aft agley.” The common military iteration of the sentiment says that no plan, however well devised, survives contact with the enemy. And former heavyweight champion Mike Tyson explained, in the least poetic fashion possible, that everybody’s got a plan until you bust him in the mouth.

There’s a lesson in here for businesses, even those that aren’t involved in actual combat: Nothing wreaks havoc with strategic planning quite like hard times. We’ve all got a plan, a vision, a dream, but these plans have to navigate whatever reality throws at us, and the more adverse the conditions the harder it is to stick to the course.

One of the biggest problems is that when things aren’t going well, any temptation becomes more alluring. I once worked with a firm that specialized in top-end, highly customized e-learning solutions, and thanks to a very talented team and an outstanding offering things were going pretty well. Until the post-9/11 crash, when all of a sudden training budgets began disappearing. Projects that had seemed all but sewn up got delayed or cancelled. Making things worse, the firm had just undergone a good bit of expansion, adding a few people to met the demand and moving into larger offices so we didn’t all have to sit on each other’s laps.

Our strategy was clear, but at the same time everyone on the team had significant transferrable skills that were of value well beyond the e-learning sector. Slowly, over a period of months, our bizdev conversations and sales pitches began to shift. But the shift was driven by need and opportunism, not strategic planning. It got to the point where I’d joke that we’d walk into a pitch as an e-learning firm and an hour later we’d be a trucking company. This was an exaggeration, but sadly, it wasn’t much of one. We needed business, we had the talent, so if a potential client said we don’t need A, but do you have any expertise in B, the answer was “absolutely!”

It became clear that opportunism was the enemy or strategy, and over time I could feel our loss of focus in ways that were almost tangible.

Given the nation’s current economic situation, it’s easy to imagine that a lot of companies in a lot of industries are wrestling with this very dynamic. They want and need to remain focused, but at the same time rigid adherence to strategic plans are of little value if you’re out of business. So what to do? How can you be adaptive without letting rampant opportunism suck the focus out of your organization? A couple of suggestions.

First, revisit your plans regularly. Every couple of weeks make sure your company’s leadership touches base with the vision and long-term goals. Even if these catch-ups are brief and amount to little more than ritual, it’s important to remind yourself periodically who you are and who you want to be.

Second, allow plans to evolve where appropriate. Sometimes a tough economy is nature’s way of telling you that there’s a better path you could be following. Down cycles require innovative thinking, and there are lots of examples of companies that wound up succeeding in ways their plans never predicted. Ray Kroc, for instance. Nike. Hewlett-Packard. They key is to control the evolution of your business direction instead of letting it be whipped around by market turbulence. Change is fine, so long as it’s directed change that doesn’t require you to lose touch with who you are and who you want to be.

For example, as you’re thinking about your plans, ask yourself what your goals really are. You may have charted a course to be the largest provider of widgets in your state, but when you begin peeling the onion you may find that what really energizes you has nothing to do with widgets at all. Maybe what you really covet is industry leadership, and you’d be just as happy doing that in the closely related thingamabob market, which happens to be looking like a stronger play long term than widgets.

Change can be a powerful force for success in the life of your company, and if I were to observe that crisis opens the door to opportunity I’d hardly be the first. But there’s an important balance to be preserved, and it begins with learning how to take advantage of opportunity without being swallowed whole by opportunism.