CNBC Jim Cramer said Thursday that long-term investors must steel themselves as the stock market tanks on President Donald Trump’s sweeping tariff announcement.

During “Squawk on the Street,” Cramer said, “If you were OK in 2007 and 2008, it came back,” referring to the financial crisis and how the market did eventually recover.

“It did take until 2013 to get the money back,” Cramer said, acknowledging that investors who need their money now, such as retirees or those nearing retirement, are “in limbo.”

“But don’t sell, just hold,” Cramer concluded. In fact, following these comments, he actually bought more shares of two stocks for the CNBC Investing Club portfolio that should not be down as much as they are.

The current market plunge is a price-to-earnings ratio lowering event, he said. “That’s what’s happening. Once that happens, then I think you really have to start thinking, ‘That’s interesting.’ It will get there.”

P/E ratios are a standard way on Wall Street to evaluate what investors are willing to pay for stocks. The current forward multiple on forward earnings (next 12 months) for the S&P 500 is just above 20. The trailing P/E, which looks at the past four quarters of reported earnings, was closer to 25.

Cramer used the financial crisis as an analog and reflected on the advice he gave then. “I came on the ‘Today’ show in 2007 and I said, ‘If you need any money in the next five years, you should sell.’ And it was a great call.” He continued, “Then I came in at the ‘Haines bottom.’ Mark called me, the late Mark Haines, and he said, ‘You got to get on board. It’s a really good level to buy.’ I came out and did that.”

Mark Haines was a CNBC anchor credited with calling, while on air, the financial crisis market bottom on March 10, 2009. The legendary call has become known as the “Haines bottom.”

Cramer has always had great respect for Haines, whom he battled with over stocks each morning back in the day. On Thursday, Cramer said the problem with the advice he gave back then is people only remember the sell call and not the call when to get back in. He has cautioned about this phenomenon over the years as a reason not to try to time the market with big sweeping trades. That’s because investors who want to get back in eventually have to be right twice: First on the sale and second on the repurchase at the bottom.

With that mindset, Cramer was looking at Thursday’s market sell-off more through the lens of how he can take advantage of everyone else’s fear and buy into names that can weather a Trump tariff environment.