Jim Cramer: Single Most Important Investing Concept By: CNBC.com News February 11, 2013 at 18:02 PM EST There are lots of concepts to keep in mind as you navigate the market. But of all them, Jim Cramer says this is most important. Read More >> Related Stocks: Energy Select Sector SPDR FINANCIAL SEL HEALTHCARE INDUSTRIAL SEL S&P Retail SPDR TECHNOLOGY