Your illusion of being a rational person is supported by the fact that sometimes you do act rationally. All the little things you do every day are probably rational. You brush your teeth to avoid cavities, you set your alarm clock to wake up on time, and so on. So your daily experience of living involves making one rational decision after another. You also believe—incorrectly—that you are rational when you make the big decisions about love and money and lifestyle. But that’s mostly a result of cognitive dissonance and confirmation bias.
