Say the average length of a novel runs around 80,000 words. Contained in those 80,000 words are likely thousands of sentences. How important could one line out of thousands possibly be?
When it comes to first lines, I think you'll find they're nearly as important as successfully pitching the One Ring into the fiery depths of Mount Doom (or, to be a little less dramatic, as important as having matching seam allowances when piecing a quilt or wearing a pair of jeans that don't squash the life out of you during a long car journey), but let's explore that theory, shall we?