As the Dow Jones industrial average dragged stocks down 666 points on Friday in an ominous end to the worst week for stocks in two years, CNBC's Jim Cramer wanted to vet the upside. After months of an endless bull rally where it seemed like stocks could only go up, not down, Cramer was not surprised to see the market's first tangible decline spark sheer panic. "I'm not disputing for one moment that today was anything but plum ugly, but let's put a huge caveat in here. The absolute numbers for this decline may sound big. Hey, there was a time back in 1987 ... where a down-500-point day was a crash," the "Mad Money" host said. "But here's the thing: the absolute numbers, they don't matter. Only the percentages are important," he said. When the Dow lost 500 points in 1987, it was a 22 percent decline. But this market's 666-point nosedive only amounted to a 2.5 percent decline — still "awful," but not a crash, Cramer said.

The backdrop

With that in mind, the "Mad Money" host laid out some heartening facts about the market for investors who might be worried about what comes next. "We are in the midst of one of the greatest economic expansions that I've seen in decades. We are in the most pro-business, pro-profit-creation moment that I have ever seen. We have a president, love him or hate him, who's been relentless in his embrace of the stock market," Cramer said. "Aided by tax reform, our companies are more flush than any time I can ever recall." Cramer noted the still-prime possibility for company-led stock buybacks and capital returns, both of which would satisfy shareholders and help the market recover from its Friday drop. To add to the strength, Friday's jobs report from the Labor Department showed robust hiring, with unemployment sitting at a low 4.1 percent and wages starting to tick up.

Should you buy?

But investors who want to be brave and jump into the market now should think twice for a few reasons, Cramer said. First, with all of the optimism in the bull market, many investors have already bought in and may not have the cash to buy more, Cramer said. "We need to burn off some of the euphoria before we go all in," he quipped. Second, Cramer advised investors buying for their retirement portfolio to wait until next week to enter the market. "In fact, I'd go so far as to say you're getting a terrific chance to slowly put some money to work at lower prices than you even dreamed of," the "Mad Money" host said. Third, some investors might need to sell in order to buy, Cramer said, insisting that they sell "anything that's gone up so much that you feel like a pig for owning it." "Sell enough so that you'll feel better if the stock gets hammered, not worse," he advised. "I would be a seller of the oils — they act terribly. Maybe we've seen the high in oil barring some sort of geopolitical event. And you know what else I'd get rid of? How about stocks that haven't moved much in the last few months? You know why? Because they ain't never going to move."

What to buy

When the market is declining, Cramer likes to fall back on secular growth themes that remain strong no matter how stocks behave. His favorites were the defense stocks, but he also liked the aerospace, cloud and internet of things names, singling out Amazon as "the best-in-business" for tech. Cramer added that the banks were good buys that are riding a wave of "nirvana" thanks to rising interest rates. "Everything else? There will be plenty of time to buy others, including some retailers, ... some industrials [and] some special situations, companies that are helping themselves that got thrown out with the bathwater," Cramer said.

Final thoughts

"So let me give you the bottom line from Minneapolis: we were due. It's not the end of the world," the "Mad Money" host concluded. "However, it might be the end of the fairy tale world, which is just as well. People, it has been too easy. It is about to get hard. Not impossible, but a heck of a lot harder than it's been."

WATCH: Cramer advises investors after 666-point Dow drop