
That said, writer's block is the main reason why I've been writing more than one project at a time. I do halt on unexpected moments - and they will be plentiful as creativity runs wild - and it may take days, weeks or months to learn how to deal with it and resume writing. It's perfectly normal and expected... have you never hit a moment in a campaign where you think "what now, how exactly do I portray that moment"? I assume, and it's a wild guess but a perfectly plausible one, that "developer's block" is the main reason behind so many campaigns being cancelled.
And indeed, it takes a lot of energy to overwhelm the block, but once you do so, you know you're closer to completing it - a big sense of achievement ensues.
I also partially agree with Mesk on the comments regarding money and getting paid. If there's money involved, chances are there'll be deadlines, and that's an absolute killer of passion and motivation. So, while getting money itself probably isn't that bad, the deadlines and external control over your work that arise from it definitely are.
---
I'm also finding some of Des... Marco's statements on development really interesting. For example, the one related to the main character, who will usually share his own beliefs. I personally spread elements of my real self to the main hero cast - and, depending on circumstances, to the villain cast as well. Alien elements to myself, as in, features and beliefs exclusive to people I know in real life or even an outstanding fictional character, are also components of these key characters. Note that this process is not exactly completely conscious, as the characters, and sometimes entire storylines, appear out of a sudden in my head.

However, like yourself, I do put a lot of value in internal consistency, the constant asking of "why do person X do this", "how would Y deal with it" and so. More than crafting the original plotline, revising and polishing it as often as possible seems to make a difference.
I just felt like writing and adding something to the topic, anyway.
Oh, and just not to say that I've ignored another prominent discussion in this topic... sex is awesome. As long as mailmen, goats, tentacles or pineapples aren't involved. Yeah, that.