It's like PG says in his essay,"The Island Test": "The notebook and pen are professional equipment, as it were. Though actually there is something druglike about them, in the sense that their main purpose is to make me feel better. I hardly ever go back and read stuff I write down in notebooks. It's just that if I can't write things down, worrying about remembering one idea gets in the way of having the next. Pen and…
At least in my personal case, I've solved the hardest problems while being asleep.