Stocks roared higher on Monday, but one legendary hedge fund manager isn’t breaking out the champagne just yet. Optimism that COVID-19's spread may be slowing powered the market’s impressive rally, with the Dow Jones closing the session up by over 1,600 points. That said, it may be too early to start toasting to the market’s recovery and the end of dramatic volatility.Billionaire Steve Cohen is warning staff of his investment firm, Point72 Asset Management, to stay cautious as stocks rebound from the COVID-19-driven sell-off.