It can be shown that maximum diversification is achieved by holding each stock in proportion to its value to the entire market (italics added)... Hindsight plays tricks on our minds... often distorts the past and encourages us to play hunches and outguess other investors, who in turn are playing the same game. For most of us, trying to beat the market leads to disastrous results... our actions lead to much lower returns than can be achieved by just staying in the market.