If it's any consolation, I had about $100k invested when the 2008-2009 crisis happened. It was utterly terrifying. The news pundits were overlaying Great Depression charts with current charts and asking when the next 30% drop would happen. Layoffs everywhere. Numbers tanking left and right. Household name banks were disappearing. I lost more to the stock market in 2008 than I earned! Years of savings seemed to evaporate overnight. Even worse, if I lost my job and couldn't get another I'd be broke within a year!
I decided to invest cautiously for the next 9 years, keeping at least 20% in cash and another 30% in low-beta preferred stock, waiting to buy on the next drop. It seemed reasonable at the time.
The media helpfully informed me about how the national debt was spiraling out of control. Congress kept threatening not to renew the debt ceiling. Interest rates could rise at any minute. Commodities were crazy. China's market, which was surely a bubble the whole time, got scarier and scarier. Then Donald Trump, an obviously mentally ill person, was elected. PE ratios stayed above average, so I held back some more.
Now it's 2017, and I look back on a history of selling low and hoarding cash. My NW is $500k, but I realize I left at least $200k on the table by not staying invested over the years in a total market index fund like VTI.
By playing it "safe" for 9 years, I earned myself another FOUR YEARS of labor before financial independence. In other words, the effect of staying partially out of the market all these years has been the same as or worse than the financial crisis itself.
In the long run, the crisis cost me nothing. The shares I held onto recovered in due time. In fact, I even harvested some tax losses.
What I did with my own judgment, however, has permanently set back my aspirations. By playing it "safe" and waiting for a better time to buy, I lost a decent chunk of my remaining lifetime to a beige cubicle.
What would a 10% correction cost you at this point? The psychological angst of seeing a $500 paper loss? Learn to fear my outcome as much as you fear the correction, and you'll be all the wiser for it.