Investors around the world admire Warren Buffett and the impressive returns he's brought to Berkshire Hathaway shareholders. But in today's market, there's one piece of Buffett wisdom that's most important to remember.

In the following video, Dan Caplinger, The Motley Fool's director of investment planning, points to Buffett's statement that "you only find out who is swimming naked when the tide goes out." Dan notes that stocks have made a huge bull-market run over the past five years, making it easy for anyone to make money in the market. But what distinguishes the best stocks from the rest only becomes clear when markets go flat or pull back. Dan takes closer looks at Rite Aid (RAD 20.00%), Fannie Mae (FNMA 1.51%), and Freddie Mac (FMCC 1.63%), pointing out the dangers involved as well as the possible returns. Yet he also points out that even stocks that have clear potential for huge growth, such as Tesla Motors (TSLA -1.92%) and Micron Technologies (MU -4.61%), have to justify their share-price gains with fundamental growth. Dan concludes that you need to preserve wealth as well as finding ways to make it grow, and the right balance will keep you on track to meet your financial goals.