Finding a Balance between Acceptance and Rejection--Seesaws in the Writer's Life

At a writer's conference recently, I sat in the audience and listened to a panel of four agents.  They fielded questions and then began to speak about the of-so-difficult process of acceptance and rejection.  Expect rejection as part of the journey, they said, in many different ways. 

Why does an agent "fall in love" with a book?  Why doesn't she or he?…