Last week in a New Jersey school, a 4th grade girl (Emily?) asked an unusual question. She said she often started to write, then tossed away her start, tried again, discarded it again. That was her problem. I recall saying two things: 1) that maybe she was actually a good writer (her teacher, seated nearby, murmured, "Yes, she is!) and maybe she was just being too critical of herself; 2) I said that if my parents had saved my 4th grade writing, probably no one would be impressed by it, and say, "This person is going to be an author!"
My comments weren't very helpful for her specific question, but I felt I had to go on to another student's hand-in-the-air. Ever since I've had those "I wish I had said" thoughts. Ideally, we could sit together for half an hour and talk, writer-to-writer. I would ask her specific questions about the problem she posed. And, at least, I'd give her this advice: Try to give up on writing perfect sentences. When I write, my first try at a sentence is often far from perfect. Some might be called a "sloppy sentence." But I know that I can and must go back to it, and try to make it better. Revise! Edit! And, after writing many books and getting advice from many editors, I'm pretty good at it. But that is not true of most 4th graders. So, I'd try to leave Emily with the idea that a not-very-good sentence can be made better, and eventually she will probably learn to be a good editor of her work.