What if some days I resist that chocolate cake, and at other times I have a bite? Or two?
For me, it works like this......
Determine your scores for "hunger", "self-image", "happiness", "the day I had", "who else is around", "amount of chocolate left", "time since last chocolate eaten", "weather conditions".....and so forth.
Add those scores together....or possibly multiply, or divide, or some other complex formula.
If your sum total is equal or greater than your current "required score" to eat chocolate, then you eat a piece. If your score is over by 10%, you eat two pieces. If your score is over by 50% - or if you are American
- you eat the whole damn bar.
Every variable fluctuates constantly, as you can imagine. And depending on those variables, the "score required to eat" will vary as well....as well as (perhaps) the relationships between variables.
Consider this.....clearly some days you eat a piece of chocolate, other days you resist. Why? What happens to one's "will" that means one day it is "strong enough", another day "too weak"?
Free will has to explain a whole lot of questions as to why a person does something on a particular day that they did not do the week before, which the believer in a deterministic universe has a simple answer for.