Stocks are wobbling amid a U.S. war with Iran, and investors may feel anxious . But volatility is a common feature of the stock market. Indeed, drops of 1%, 2% or more in a given day — though they may feel nauseating at the time — happen more often than you may think. The S&P 500 U.S. stock index, for example, has fallen 1% or more on 1,001 days over the past 30 years — or, about 33 days per year, on average, according to a Morningstar Direct analysis of market data since 1996. Over the same