Writers need patience.
Writers need patience when they first start out. When you write your first story, hey, that's great! You're on your way! Now, go write five whole books, pour sweat, blood, and tears over them until they're the very best they can possibly be, and then put them all in a box in the garage because only now are you ready to write something worth publishing.
Writers need patience when they finally get to that book that's going to be the one. Books are like delicate little plants growing in a greenhouse in early spring. Send them out too soon, send them out before they're ready, and they die. It is so hard to wait, so hard to do one more revision, so hard to think it all through and think it all through again. But, with time, the ideas grow stronger, the characters grow stronger, the story grows stronger.
Writers need patience when the time comes to submit. Researching agents and editors, preparing query letters and synopses, all of this takes time away from writing. And then the waiting. The eternal waiting. Six weeks, eight weeks, three months... yes, you can draft a new novel in the time it takes to hear back on a submission. I know. I've done it.
Writers need patience as their agent or editor asks for revisions. I have a friend who was asked to do four re-writes before signing a contract, and then another four re-writes after. It takes years, years upon the years already spent in learning the craft, to create a book and get it ready for printing.
So the next time you hold a good book in your hands, think of all the patience that went into it.