Why do we take blame and criticism so personally?

I ask this because I have witnessed it in others - and exprerienced it myself. Its an immediate 100 foot wall that pops up out of no where. Sound the sirens, let loose the hounds... its a mechanism that instantly ignites within us to protect this thing called 'ego.'

Where does it come from? Why is it there? How do we remind ourselves the attacks never really hurt or touch the 'real' me?