All writing is made up of three elements:
NARRATION: The writer speaking directly to the reader. It is the backbone of the story. Keep it active and the story will move. Use it to show rather than tell. Verbs are the key.
DIALOGUE: A character speaking. Aside from an excellent tool for character development, it speeds the pace of the work.
INTROSPECTION: The opinions, fears, deductions, judgments, expectations, or other internal thought processes peculiar to the viewpoint character. It is, by far, the best tool for character development. The danger is, it slows. Large blocks of it will drag the pace to a crawl. Do not confuse introspection with internal dialogue.
A balance of these elements is necessary for a well written story.