Tip of the Week: Do not overextend yourself.
This advice is just as true for writers as it is to marathon runners and stockbrokers. You do not want to write yourself to exhaustion. And I don't mean just physical exhaustion. I mean to the point that you hate your characters so much that you want to kill them all off in book 4, not because it's germane to the story, but because it would just be so gosh-darn fun. It's when you've promised to write 7 reviews, 2 magazine short stories, and to get that novel rewrite to your editor all in the same week. It's when you sign a book deal for a 8 book series when you've only planned out the first 2 books. Overextending yourself can drive you insane and push your stress level to new, unfathomed heights. You know your limit. Listen to it. When you find yourself reaching it, pull back. If you find you're going to miss a deadline, give your editor or publisher lots of advance notice, and then just deal with it. Trust me. Your characters (and editor) will thank you later.