Here is an excellent article about creativity.
Creativity is a combination of these three elements.
The Dreamer is necessary for creativity in order to form new ideas and goals. The Realist is necessary for creativity as a means to transform ideas into concrete expressions. The Critic is necessary for creativity as a filter and as a stimulus for refinement.
There are a lot of self-help books and experts that tell you the dreamer is the only one you need. That the realist and critic are evil and need to be stopped. Think of how often imagination is extolled as fragile flower to be cherished and never judged. Think of how often people tell you to silence your inner-critic.