Writing with Feeling While Under Pressure

I've read many books lately where it was apparent the author was stressed, burned out, or under too much pressure to get the book done. The books fell flat in one (or more) of many ways. Ways such as: the romance not paying off, the tension not being high enough, the main character not being involved in the solution, the humor falling flat, etc.

I don't have answers for how to prevent this, and am wondering what you all think. Sometimes you DO have deadlines. Sometimes you DO have people waiting for you. And to me, it's important to keep agreements and goals and meet deadlines. So how does a writer manage to put something together that is emotionally satisfying, even when they're burned out?

Think about it. In every single other profession, you're expected to put forth quality work even when you hate your job. You don't get paid otherwise. And bosses, clients, patients, etc., won't wait patiently for you to get excited again. Why is it that many artists feel they're different in this regard, and again, what can we do to write with power when we're in this type of situation?

Like I said, I don't have the answers. I'm hoping all of you do. :-)