Some thing are up to us, some are not. From this principle, Epictetus and the Stoics build up a great deal of relief from garbage. That which is not up to us is of no concern, we cannot do anything about us but we can protect ourselves against much of the effects, but that is a topic for another day.
Now what is up to us. The lowest form is assent to a simple proposition. Eat his, not that. No sugar, no grains gives a great deal of relief. It is up to me if I take the next bite or go away. I cannot sit in front of food and not eat. I can go away. If it is too smokey in the kitchen, leave. What others think is not up to me.
It is our culture and environment that creates these unhealthy situations. I can only live in my environment.
Choice is always up to me. The problem arises when I want something, and I chose it. But hold on, desire is up to me also. There we have the big three, assent, desire, impulse, and all else is built on those. Taking thing back to first principles shows what the problem may be, uncontrolled desires, or lack of training about control of desire.
Now where is there training available about desire control. Marcus 6.13 talks about it, the dead body of an ox, the seeds of trees, fruits of a weed, picked, soaked in HFCS and dried, the fat in the lactate of bovines, separated and congealed, or fermented the gut of a sheep; not to appetizing. (beef, nuts, dried cranberries, butter, cheese)