More Videos:

Cramer's 'Mad Money' Recap: The Market and the Machines

Search Jim Cramer's "Mad Money" trading recommendations using our exclusive "Mad Money" Stock Screener.

NEW YORK (TheStreet) -- There was a time when our stock market was held hostage by other markets around the globe, but that time is over, Jim Cramer announced to his "Mad Money" TV show viewers Thursday as he opined on a lackluster trading day on Wall Street.

Cramer explained the U.S. now has the strongest markets on Earth, which means that negative news like that out of Japan today, can simply be shrugged off as noise. The U.S. is far from having the strongest economy thanks to a lack of hiring, but no one can question the strength of the stocks that are linked to terrific companies that are outperforming expectations daily. When a stock like Hewlett-Packard can deliver a quarter that no one saw coming, it's hard to ignore the momentum.

But that does not mean that investors need not be careful, Cramer continued, as our markets are still being controlled by an even larger force: the machines. Case in point: American Electric Power , a stock which momentarily fell by nearly 50% at the open this morning, only to fully recover minutes later. Once again, the machines went awry and investors are left holding the bag.

That's why Cramer once again urged all investors to never place market orders and always use limit orders which can only be executed at a specified price. He said those selling at the open using market orders lost 50% of their investments in the blink of an eye, and it doesn't appear that the regulators are willing to break those trades. Those using limit order,s however, were protected from the momentary carnage.

So while our markets may no longer be hostage to the rest of the world, they are still hostage to the machines, which means investors must continue to be vigilant with their money.

Executive Decision: Jack Koraleski

In the "Executive Decision" segment, Cramer sat down with Jack Koraleski, president and CEO of Union Pacific , a stock that's up 120% since Cramer first got behind the railroad in June 2010, thanks to continued strength in oil and autos.