often people think things will make them happier eg having kids when in actual fact they don't
they over estimate things
same thing happens on the stockmarket. stocks are valued on basis of earning going forward. It is all about making good forecasts. you make a good prediction and you win money you don't you lose ... simple
take CNP today
a lot of people thought that the shareprice would go through the roof when in actual fact it actually dropped
this ability to predict is the key to a lot of things whether it is guessing who might win the footy on the weekend, having children or picking a stock
