Thanks to Greg Christopher on Google+ for sharing this new finding: it seems willpower is indeed a resource that can be worn down as you exert it.
This is great news for me, as it validates my idea of the depleting (though usually renewable) Assets, which I often see as more psychological than anything else.
For example, being Tough. What exactly does Tough mean? Are your muscle fibers denser? Are your pain receptors fewer? For me, Tough means you’re good at applying willpower vs. pain. But there’s only so far you can go with that.
I also like the idea that you can be powerful for a while, but there’s a price to pay after. This works better for me, game-wise, than a character with all bonuses pre-loaded and constantly ‘on.’