Market psychology quickly turns messy around 2,855 on the S&P

As fierce as the sell-off in stocks has been, it's worth remembering they traded lower as recently as six days ago.

The worst print from last Friday was 2,855 on the S&P 500, coming right before Jerome Powell said the Federal Reserve was monitoring markets. Down as much as 3.6% today, it never got below 2,914. It would have to fall another 3.3% from its 10:30 a.m. level of 2,957 to retrace the gains that started when the central bank put out the statement.

"It feels like we're down more than we really are because of these extreme moves we've seen this week," Shawn Cruz, manager of trader strategy at TD Ameritrade, said by phone. "It's the coordinated nature that we'll get monetary and fiscal responses to this, that's what's helping out."

The week's seen historical turbulence. After alternating up and down sessions through Wednesday, losses snowballed on Thursday and Friday as anxiety intensified over the impact the coronavirus might have on global growth.

The Fed lowered interest rates by half a percentage point this week, its first reduction outside of a normal policy schedule since 2008. Last Friday - ahead of the emergency intervention - Powell issued a rare statement signaling the central bank was prepared to reduce rates to sustain the expansion.