Warren Buffett is considered to be one of the greatest investors ever; however, even he is not perfect. In fact, his company (Berkshire Hathaway) is named after one of his failed investments. More recently, his timing on the purchase of GM stock has not worked so well. Fortunately, his holding period is generally very long, thus it could turn out to be a favorable investment over the long-term. See article here, Bloomberg.
Dolvin, Steven D., "Even the Best Investors Can't Time the Market" (2012). All Chapters. 23.