"Consider what happens when you’re thirsty and drink a glass of water. The water takes about 20 minutes to reach your bloodstream, but you feel less thirsty within mere seconds. What relieves your thirst so quickly? Your brain does. It has learned from past experience that water is a deposit to your body budget that will hydrate you, so your brain quenches your thirst long before the water has any direct effect on your blood."
IMO the point she tries to convey is that the budget doesn't track actual, objective resource use, which also means that individual budget constraints are not only constrained by the actual physiology, i.e. with training (mindfulness and so on) one can move the baseline and thus e.g. stress resistance.
Not a new point either, but you'd be surprised how many people don't know their own feelings. My psych professor told countless anecdotes of patients who didn't know that the disquieting feelings they experienced when e.g. being inside an elevator were actually a panic attack.