[tim333]

To understand "rationality is not always to our benefit" from an engineering perspective it can be helpful to bear in mind the ideas of evolutionary psychology - the evolutionary pressures on brain design are towards getting your genes into the next generation, not towards being perfectly rational. For example as to who gets the girl or the leadership role the guy who says I'm the greatest and believes it has an advantage over the guy who thinks he's mediocre even if in reality both are equally mediocre. So rationality works well for engineering things, less so for dealing with humans.