3. The world's bankers did their part.
Fears that the major central banks would pull back on stimulus, despite a still-sluggish global economy, had some investors worried this spring. But the Janet Yellen-led Federal Reserve made it clear to Wall Street that it had no plans to start hiking short-term rates, now at record lows, prematurely. And yesterday, in an attempt to jumpstart Europe's economy, the European Central Bank did its part. It cut interest rates to record lows, announced new steps to boost bank lending and hinted that it would embark on a U.S.-style bond-buying program if needed.
"If Europe's economy picks up," says Warne, "it's a positive for the U.S. and the rest of the world."
Read MoreECB's Draghi announces host of stimulus measures
4. The Ukraine crisis didn't spiral out of control.
Talk of Cold War 2.0 has died down. The Ukraine/Russian crisis has cooled following new elections in Ukraine and a less confrontational approach from Russia.
5. The bearish warnings didn't come to fruition.
Predictions of a 1987-style crash or a big stock market downdraft have not come true. In fact, this week, hedge fund honcho David Tepper of Appaloosa Management toned down his concerns about stocks. Last month, he sounded a warning, saying that the stock market was getting dangerous and that he was getting "nervous." His fears at the time were the ECB's lack of urgency related to the eurozone's weak economy, the Ukraine crisis, U.S. growth concerns and worries about China. But yesterday, he told cable business channel CNBC that many of his main market fears have "alleviated."
Read MoreAppaloosa's Tepper: Chief market concerns have 'alleviated'
Market skeptics, of course, argue that complacency is again running high on Wall Street, which is worrisome. Citigroup, for example, says its proprietary sentiment tracker has moved further into the "euphoria" stage, which suggests investors are getting overconfident. And in another bad sign, Ned Davis Research says legal insider selling by corporate executives is on the rise, signaling that executives think their shares are fully valued.
But, for now at least, stock investors' lack of fear is translating into fatter gains.
Still, Warne's advice to investors is "be prepared" for the next market correction. "We don't want people be to be surprised if there is a correction," she says.
—By Adam Shell, USA Today