Rule 14 is "Take some down time." You need to let your project rest for a while sometimes. Maybe a day, maybe a week. You need to take a vacation once in a while, whether it is a day or a month.
This rule contradicts all the other rules about writing every day, I know. I am perfectly capable of writing almost every day for almost a year, but I also have found I need to take some time off once in a while. Usually, I find that what I am doing during this time off is some intense kind of thinking of another sort. For example, during the recent stretch I have been learning "Tintern Abbey," a poem of 159 lines.