"The mind is everything. What you think you become." 
– Buddha
(Image Credit: Mercedes-Benz)

The above image is a beautiful depiction of the way the brain processes information. However, one immediate caveat needs to be underlined; although the left hemisphere of the brain can be thought of as linear (logical) and the right, holistic (creative), the actual processing of information involves both sides of the brain (although it’s more localised to one side or the other depending on the task).
The left side is where we sequentially process our lives... we write lists, create plans, etc. The right is where we let our hair down... we think randomly, fantasise and listen to our intuition, etc.
If ever there was a skill that uses both sides, it’s writing. It utilises our left hemisphere’s skills of planning, organising and linguistics; and the creative skills of our of right to imagine stories, have random flashes of inspiration, and if we’re very lucky have characters who speak back to us! Like other creative forms of expression such as music and painting, it’s the interplay between two cognitive areas that makes it so endlessly fascinating and a pleasure to pursue. Writing isn’t just an activity, it’s a highly personal exploration of  the internal landscape of our minds. No wonder it's so addictive as a form of expression.