You don't need to be a rocket scientist. Investing is not a game where the guy with the 160 IQ beats the guy with 130 IQ.
Warren BuffettOne of the ironies of the stock market is the emphasis on activity. Brokers, using terms such as 'marketability' and 'liquidity,' sing the praises of companies with high share turnover... but investors should understand that what is good for the croupier is not good for the customer. A hyperactive stock market is the pick pocket of enterprise.
Warren BuffettIf you are a professional and have confidence, then I would advocate lots of concentration.
Warren Buffett