Cramer's 'Mad Money' Recap: June 30

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Editor's note: This show last aired on Dec. 26, 2008.

"Investing is all about discipline," Jim Cramer told viewers of his "Mad Money" TV show Tuesday.

He said it's not enough to know which parts of the market are working or which stocks are buys and which ones are sells. The key to successful investing, Cramer said, is to know thyself.

Far too many people invest like gamblers, said Cramer, and not even good gamblers. "Investing isn't a game and it's not random," he said.

Investors need a plan and they need to stick to it. Understanding what you're doing and why is the key. Understanding your own weaknesses and removing emotion from the equation are also crucial, but very hard, skills to master, said Cramer.

Cramer recommended investors be honest about why they're buying certain stocks. Only by having a good understanding of why you think a stock will go up, will you then know when it's time to sell, he said. "Never turn a trade into an investment," he reminded viewers.

"Be honest about your expectations, clear about your plan, and willing to abandon ship the moment those expectations are not met," said Cramer, "then you'll make yourself a lot of money."