If you consistently write 'The sun set' rather than 'The sun sank slowly in the bright western sky,' your story will move three times as fast. Of course, there are times you want the longer version for atmosphere - but not many. Wordiness not only kills pace; it bores readers.
The truth is, you have about three paragraphs in a short story, three pages in a novel, to capture that editor's attention enough for her to finish your story.
You must learn to be three people at once: writer, character, and reader.
Words that add no new information or aren't repeated for emphasis are just padding. A sentence may carry three or five or eight of them, each one as unnoticeable as an extra two ounces on your hips but collectively adding up to a large burden of fat.