I like to write in the morning, particularly if I am writing something long and difficult, something that requires a very clear mind. However, if I start in the morning but am not able to get much written after several hours, I will feel like I have lost my momentum and for the rest of the day I probably won't be able to write much either. The following trick that Haruki Murakami uses, which he mentions in his book What I Talk about When I Talk about Running, may help solve my problem:
Sometimes I run fast when I feel like it, but if I increase the pace I shorten the amount of time I run, the point being to let the exhilaration I feel at the end of each run carry over to the next day. This is the same sort of tack I find necessary when writing a novel. I stop every day right at the point where I feel I can write more. Do that, and the next day's work goes surprisingly smoothly. I think Ernest Hemingway did something like that. To keep on going, you have to keep up with the rhythm.