Warren Buffett believes his best deals during the economy's biggest belly flop since the Crash of 1929 may well turn out to be the ones he didn't do.

Buffett slammed the door on one opportunity after another during the most harrowing stretch of his storied career. That impulse, he says, left him with the financial firepower he needed last month to strike the biggest deal he has ever done - Berkshire Hathaway's $26.3bn (€17.9bn) purchase of railroad Burlington Northern Santa Fe.