Many years ago there's a hedge fund manager named Monish Babbri and he was having dinner with Warren Buffett. He asked Buffett, what happened to Rick Gurren? And Warren told him this fascinating story. In 1973 and 1974 the stock market went down almost 70% in those two years. So Rick got margin called. He sold all of his Berkshire stock back to Warren. Naseem Tyler put it this way: Having an edge and surviving are two different things. The first requires the second. You need to avoid ruin at all costs.