Humans have a need to try to exert control over that which is inherently uncontrollable. And, in the end, our own humanness conspires against us. In the face of unseen danger, we become bold. When we face imminent danger or actualized danger, we react instinctively rather than rationally. In the perception of safety, we tend toward greater risk-taking.
Humans generally lack the cognitive ability to properly measure risks and rewards.
In investing, those who have even a slight advantage in recognizing risks and rewards will have a Darwinian advantage that will be amplified over the length of a career. In some ways, some of the most rational owners are ones who recognize, either actively or passively, that they are unsure of their ability to beat the market. But, a good number of people make a big mistake here by entrusting their capital to an investment manager who, in most cases, is also unable to beat the market, because he or she has the same cognitive irrationality that all humans have. In fact, studying Warren Buffett's investing career, it has been said that his greatest advantage is not one of analysis, but rather his willingness to be anti-social. These are the people who have more knowledge and more training than the vast majority of investors.