So... I was thinking about writing similes. Not about the act of writing the-things-that-aren't-metaphors, but of similes of writing.
Writing is like shopping at a thrift store. Words and stories are never "new", never completely original. They all have a history, all have been used before. What makes thrift store finds, and "new stories," memorable is the way you put it all together.
What are other writing similes? Leave yours in the comments. More that I can think of:
Writing chick lit is like attending a wedding. You know that the bride and groom will exchange vows, but everything else is a toss-up.
Writing is like mowing the lawn. It may seem like you burn out and all the grass is gone, but wait a few weeks and bazoom! the lawnmower will roll again.
Writing is like riding a horse. It can be a quiet stroll or a boisterous rollicking ride, but you never know what to expect and you are never fully in control. You also might get kicked in the rear.