As a preface none of this really has solid scientific research to back it, just my interpretation of things I've read.
A few years ago it popped into my head that excess cortisol makes you do things you don't really want to do. So, if you can control cortisol, you can attain something close to free will. At the same time cortisol isn't some devil hormone, excess of any hormone can lead to bad things, so homeostasis is what you're after I think.
What can stop cortisol from making you snap and do something you regret?
Oxytocin, serotonin, dopamine.
How do you stimulate these hormones?
Meditation, things you truly enjoy, achievement, togetherness, touching. The Meridian Matrix alchemy would probably be really helpful.
I'm on day 8 of a fast and I've never gone this far before. Knowing the voice telling me to break the fast and say screw it just eat something is probably cortisol talking has helped. This is also the first time I've used electrolytes and I feel it helps control ghrelin, but ghrelin really isn't that hard to suppress it's just a dull pain in the stomach.