"Baron Rothschild, an 18th century British nobleman and member of the Rothschild banking family, is credited with saying that "The time to buy is when there's blood in the streets."
He should know. Rothschild made a fortune buying in the panic that followed the Battle of Waterloo against Napoleon. But that's not the whole story. The original quote is believed to be "Buy when there's blood in the streets, even if the blood is your own."
This is contrarian investing at its heart - the strongly-held belief that the worse things seem in the market, the better the opportunities are for profit.
Most people only want winners in their portfolios, but as Warren Buffett warned, "You pay a very high price in the stock market for a cheery consensus." In other words, if everyone agrees with your investment decision, then it's probably not a good one."
http://www.investopedia.com/articles/financial-theory/08/contrarian-investing.asp