Last time I made a Big Point about finishing what you start.
This time I want to stress that it is okay to stop working on a project for a few days (maybe even a few weeks) and do something else. Make no mistake, I am NOT advocating "project hopping." That's when you let your muse lead you around by the nose, starting a million projects and never seeing any of them through to the end. But, in our drive to write every day and finish all our novels, most of us (I include myself here) overlook the fact that writing is work. Enjoyable work most of the time, but still... work.
In most professions we get weekends and holidays off. As writers we are expected (and seem to expect of ourselves) that we go all the time with no breaks or vacations or stopping our forward momentum for any reason.
This is wrong.
Our brains need time to rest. Our creativity needs time to refresh. Our hands need time to recover. In general, taking a break for a day or two every few weeks will not kill your writing discipline nor will it make you any less committed as a writer. I do not want to encourage laziness. Writing is work and should be approached as such. But, since it is work, it can be put aside for a "weekend" or a "vacation" to allow yourself time to breathe and relax and remember why you're so excited about this project in the first place.
I still think that writing every day is important. Setting concrete goals (words per day, pages per day, chapters per week, whatever works for you) is important. Knowing when to take a break is equally so.
Don't write yourself into exhaustion. (Writer's exhaustion is, I believe, the all-too-common cause of so-called "writer's block".) Take a break. Read a book. Take a walk or go on a picnic.
Then come back and write your ass off.