What is it when the tree withers and the leaves fall? Complete exposure of the golden wind.

To a Buddhist, this thousand-year-old Zen koan speaks volumes about the passing of seasons, the fleeting nature of life itself, natural beauty, and much more. A modern-day investor's lesson is much simpler: The withering wind of market panic exposes new opportunities.

Wax on, wax off, young grasshopper
Don't worry, I'm not about to go all mystic on you. The simple truth is that panic rarely accomplishes anything good.

For example, let's pretend that you caught wind of multiple sclerosis wonder-drug Tysabri early on and invested in Elan (NYSE:ELN) back in 2004. Tysabri had just been approved for MS treatment, the company's pipeline had some promising Alzheimer's drugs and even some medical nanotechnology -- life was good.

Then a couple of patients caught a rare but fatal brain disease. Tysabri was temporarily taken off the market, and Elan's stock collapsed. Selling out in a panic-stricken daze would have locked in a loss of 80%-90%. Tysabri partner Biogen Idec (NASDAQ:BIIB) saw a smaller (but still very painful) 40% swoon at the same time.

Or, you could stand back and take a calm look at the situation. A handful of serious side effects among more than 2,000 patients was a roadblock, but not a death sentence. This would have been a great time to double down on Elan; in fact, it's where I bought my own shares. I sold a little bit of that stake in May 2008, locking in a four-bagger return only because Elan's stock had started to take over my portfolio.

We're not done yet
And now Elan is back down again on general recession fears, plus another couple of PML cases. No use rushing into a decision, though. There was an eight-month window of awesome opportunity last time around, and I don't expect any massive rebound in the next few days or weeks.

Patience. What is the sound of one stock falling? Sometimes it's the sweet melody of great future returns.

I could tell you similar stories about robotic surgery pioneer Intuitive Surgical (NASDAQ:ISRG), superhero creator Marvel (NYSE:MVL), or online giant Google (NASDAQ:GOOG). Most have happy endings, while a few stories are still being written. In all cases, I've had plenty of opportunity to panic and miss out on great gains. But I benefitted the most when I doubled down or simply stayed the course, after a bit of research. That's the secret of a happy portfolio, if you ask me.

Further Foolishness:

Elan, Google, and Intuitive Surgical are Rule Breakers picks. Biogen Idec and Marvel are Stock Advisor recommendations. Try any of our Foolish newsletter services free for 30 days.

Fool contributor Anders Bylund owns shares in Elan, Marvel, Intuitive Surgical, and Google, but he holds no position in (um, what's left?) Biogen. You can check out Anders' holdings or a concise bio if you like. The Motley Fool's disclosure policy is the sound of one hand clapping.