Byron Wien, one of the most respected voices on the market, has a bullish outlook for 2014 but sees the rally taking a serious breather as euphoria turns to disappointment.
"What's going to cause it is that everybody's on one side of the boat here," said Wien, vice chairman at Blackstone Advisory Partners. "Almost everybody's made good money—maybe not 30 percent last year—but everybody was up ... and people are generally feeling pretty positive. There's almost a euphoric mood."
Wien said it won't take much to turn this manic high into a manic low.
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"When investor sentiment is as positive as this, [the market is] usually vulnerable to any kind of a disappointment," he said. "There could be some earnings disappointment in the fourth quarter. And the geopolitical situation is still, in my mind, pretty unsettled. So you never know what it's going to be. But you do know that when sentiment is euphoric, the market is vulnerable."