No one knows why willpower can grow with practice but it must reflect some biological change in the brain. Perhaps neurons in the frontal cortex, which is responsible for planning behavior, or in the anterior cingulate cortex, which is associated with cognitive control, use blood sugar more efficiently after repeated challenges. Or maybe one of the chemical messengers that neurons use to communicate with one another is produced in larger quantities after it has been used up repeatedly, thereby improving the brain’s willpower capacity.
Here's a little bit of fiction I wrote a few years ago about infinite will: "Desire Magnitudes". Excerpt:
I tear open my package, and, as is typical for ET merchandise, the accompanying literature is indecipherable trash. Fuck it. I pop a pill and wash it down with some hot sludge. I'm not real sure what to expect, but I'm figuring on an ingestible analogue to my previous surgery. I'm figuring nanobots are going to modify my frontal lobes allowing for the simulation of an indefinite number of ersatz consciousnesses to deal with an indefinite number of annoying distractions. Wrong answer, dude. That is not what this pill does to me at all. Just a few seconds after swallowing, the pill establishes various interfaces with my brain, and I know my way around my cerebrum well enough to know what's what. The first interface established between the nanoprocessors and my brain is through the visual areas of occipital cortex. A translucent blue rectangle pops into my field of view. White alphanumerics scroll from top to bottom. It's extraterrestrial at first, but as the pill coordinates the visual processing with the semantic association networks in my left temporal cortex, the text writhes into recognizable English:WHAT DO YOU DESIRE?