Yesterday was a tough day in the markets, with the Dow falling 199 points. But, if you follow some of the legends of finance – such as Carl Icahn, T. Boone Pickens and The Blackstone Group's (NYSE: BX) Steven Schwarzman – you will notice that they are getting aggressive.

Keep in mind that these guys have been through multiple market cycles. And, if history is any worthy benchmark, it's during times of instability where the big money is made.

Pickens is focusing on the energy industry. He sees major demand/supply imbalances and is buying various stocks. He is also interested in natural gas and alternative fuels.

As for Icahn, he's doing what he does best – shareholder activism. He senses when companies are vulnerable and seems to relish an attack on corporate managements and boards. Of course, he's gearing up for a fight with Yahoo! (Nasdaq: YHOO). Interestingly enough, he persuaded Pickens to buy 10 million shares.

And, with Schwarzman, he's buying up the bank debt of companies that went private. Because Blackstone sees many deals, it has an extensive database of opportunities.

In other words, the legends of finance are confident in the long-term. They are making some big bets -- based on lots of experience and due diligence -- and not listening to the short-term noise. All in all, these are some valuable lessons for investors.

Tom Taulli is the author of various books, including The Complete M&A Handbook and The Edgar Online Guide to Decoding Financial Statements. He also operates MergerBook.com.