The Self Illusion: An Interview With Bruce Hood | Wired.com:
"LEHRER: If the self is an illusion, then why does it exist? Why do we bother telling a story about ourselves?

"HOOD: For the same reason that our brains create a highly abstracted version of the world around us. It is bad enough that our brain is metabolically hogging most of our energy requirements, but it does this to reduce the workload to act. That’s the original reason why the brain evolved in the first place – to plan and control movements and keep track of the environment. It’s why living creatures that do not act or navigate around their environments do not have brains. So the brain generates maps and models on which to base current and future behaviors. Now the value of a map or a model is the extent to which it provides the most relevant useful information without overburdening you with too much detail."