For a long time we’ve known that we’re far more sensitive to negative feelings than to pleasant ones. In gambling language the rule of deterrence might be stated as, “The fear of losing outweighs the pleasure of gains.” The pain of loss is quantitatively about double the pleasure we experience from reward. The psychological name for this deterrence is “loss aversion.” Loss aversion is not a flaw. Extensive research shows it to result from the very way our brain is structured. Once the evolving brain hit upon a really useful program it burned it down to the level of our DNA. Fear of loss is highly instructive, and error a powerful teacher, and so we learn not to court its pain.