How do you write when you're not in the mood?

I'm not a writer,I don't make my living by writing. But I do depend on writers to do what I do. I work with writers on a regular basis.
What intriques me is how writers can consistently write when called apon to do so. I mean don't writers have days when they feel down or uninspired? How can you guys/gals do it? If you don't feel good about where you're at on a particular day headwise,then how can you produce good quality work when you'e just not into it?

Is it simply just a matter of...

How do you write when you're not in the mood? WordPress ...