The stock market rallied on Tuesday , the last trading day of March, inspired by hopes for an end to the Iran war. But it was not an easy month for investors. In March, the S&P 500 , Dow Jones and Nasdaq indices each fell around 5% — capping off a losing quarter. Investors may want to brace themselves for more dramatic swings: The markets are poised to be "extremely sensitive to headlines, both positive and negative," said Jack Manley, global market strategist at JPMorgan Asset Management. "Now