I have always thought of writing as being essentially a solitary activity. And usually, I've preferred to think of it that way - I haven't often even been tempted by the idea of, for instance, writing a story with somebody else. (On the other hand, I have also often envied musicians just because music is/can be such a collaborative venture. (Do I contradict myself? Well, frank yes ...))

And this week, having been jump-started last, I have been working (2,000 words today! Maybe even good ones) on my own again, as my prejudice believes is the right and proper way for a writer to work.

All that said, to respond directly to your comment, having someone else around "to stoke the fire" sure seems to have been what I needed.