The longer I've lived my life, the more I believe that Executive Function is some kind of resource, it's the nebulous Willpower, a culmination of many specific facets of how you're feeling at any one time - its specifics are not known to me, whether it is a kind of discrete amount that is gained and lost, or if it is a kind of range that said factors align to allow one to be in and utilize, etc.
I'm getting better at a kind of intentionally 'rationing', or preserving or preparing, executie function for a future task, but it's still a limited resource, and I do not yet know the means by which to naturally extend that resource outside of Medications.
But it sure fucking sucks more and more to be out of it, especially when life comes at you.