What happened to stocks in January and early February is nothing new. It’s happened quite a few times in the past four years and eleven months. Ever since mark-to-market accounting was fixed in March/April 2009, these corrections have been short-lived and relatively mild. And once they were over the market went higher. It’s been a very strong bull market.
Nonetheless, few investors truly understand why things turned around so abruptly in 2009 and every time the stock market declines there is a mad rush to believe this time the sky really is falling. See First Trust