Read Becoming a Writer by Dorothea Brande. Then do what it says, including the tasks you think are impossible. You will particularly hate the advice to write first thing in the morning, but if you can manage it, it might well be the best thing you ever do for yourself. This book is about becoming a writer from the inside out. Many later advice manuals derive from it. You don't ยญreally need any others, though if you want to boost your confidence, "how to" books seldom do any harm. You can kick-start a whole book with some little writing exercise.
Hilary MantelYou learn nothing about men by snubbing them and crushing their pride. You must ask them what it is they can do in this world, that they alone can do.
Hilary Mantel