“On plenty of days the writer can write three or four pages, and on plenty of other days he concludes he must throw them away.”
This is incredibly important to remember. Sometimes you will have inspiration and be full of good ideas, some days you will not. This happens. Don’t try and force it, or you may spend ages writing a hundred pages, only to return to them to realise they’re rubbish. Don’t waste your time. Not feeling inspired? Go out and look for inspiration. Take a walk. Have a cup of coffee. It’ll come to you, don’t worry, just don’t try and force it.