The best books come from someplace deep inside. You don't write because you want to, but because you have to. Become emotionally involved. If you don't care about your characters, your readers won't either.
Those of us who write do it because there are stories inside us burning to get out. Writing is essential to our well-being. If you're that kind of writer, never give up! If you start a story and it isn't going well, put it aside. (We're not talking about school assignments here.) You can start as many as you like because you're writing for yourself. With each story you'll learn more. One day it will all come together for you, as it did for me with Are You There God? It's Me, Margaret. I'd published two books and several short stories before Margaret, but I hadn't found my voice yet. I hadn't written from deep inside. With Margaret I found my voice and my audience.