"Looking back over the 20-year period from Jan. 1, 1999, to Dec. 31, 2018, if you missed the top 10 best days in the stock market, your overall return was cut in half. That's a significant difference for only 10 days over two decades!"
What would happen to your return if you missed the 10 words days in the stock market? I bet the change would be even bigger than what the article is quoting.
I am not saying your average person should do try to time the market without having learned about how to do it. But it isn't as bad as the financial community wants you to believe.