Markets crash all the time. You should, at minimum, expect stocks to fall at least 10% once a year, 20% once every few years, 30% or more once or twice a decade, and 50% or more once or twice during your lifetime. Those who don't understand this will eventually learn it the hard way.
Someone emailed me last week asking why this is:
Have you ever wondered exactly what those initials after a financial professional’s name mean? You’re definitely not alone. The easy way to tell is to visit the Financial Industry Regulatory Authority, which provides a list of professional designations and what they mean.