For some perspective I suggest you look at the graphs on this page.
Since 1970 a similar portfolio had an inflation adjusted compound annual growth rate of 5.1% (before fees) but the one year returns have ranged between -22% and +20%. 54% of the time the annual return was between 0% and 10% but 17% of the time it was less than 0%. 4 times they stayed negative for more than 6 years and once they took more than 10 years to permanently recover.
And that is why you'll often read the advice that you don't invest in the stock and bond markets unless you are are confident you won't need the money for at least 5 or 6 years, but preferably 10 years.