The best way is always to stop when you are going good and when you know what will happen next. If you do that every day when you are writing a novel you will never be stuck. That is the most valuable thing I can tell you so try to remember it.
I do not waste my time writing pot-boilers: the pot must be boiled, and even my pot au feu has some chunks of fresh meat in it. ...I have no time to boil myself down; and anyhow I could not do so and preserve all the necessary nutriment and the flavoring on which the digestibility depends.
When I had finished the book I knew that no matter what Scott did, nor how he behaved, I must know it was like a sickness and be of any help I could to him and try to be a good friend. He had many good, good friends, more than anyone I knew. But I enlisted as one more, whether I could be of any use to him or not. If he could write a book as fine as The Great Gatsby I was sure that he could write an even better one. I did not know Zelda yet, and so I did not know the terrible odds that were against him. But we were to find them out soon enough.