To be creative you must be open, which means to be humorous (seeing the odd angle) requires an open disposition. Once you have made a decision you must be efficient: practical, linear path making.
To do both at once is to accomplish nothing: procrastination or chaos is self-defeat.
Knowing when to release from the left brain impulse of rationality and invoke the holistic story-telling flow of the right brain -closed vs open- is how even the mediocre can transcend.
To be the best, you become a conductor of groups of people, opening them and then focusing on them, letting them dream, and then motivating them to produce.