The first time I heard "The left hand is the dreamer, the right hand is the doer," it came from a conductor/ composer who was left-handed. Ever since I've thought of writers, actors, artists and dancers as left-handed dreamers though they might lift a utensil or a pen with their right hand. The right hand belonged to practical people--scientists, engineers, firemen or policemen. Law and order existed on the right while the left dreamed of the past or the future and interpreted every happenstance in a romantic way.
Many performers have begun their careers in another art form before picking up a pen or sitting down at their tablet or computer and finding fulfillment and/or success. But a large number of writers have come from fields that I would consider "doers," particularly doctors. What quality makes so many doctors vivid writers?