Theories about the ego depletion modl of self control were popular 20 years ago. Ego depletion meaning that there's something inside us, our mental capacity, that is depleted with use. Maybe what happens when we try things that are mentally hard is that what we're really depleting is blood sugar in the brain.
Why do some activities tire your brain more than others? How exhausting is poverty? And could most of the world’s problems be solved with a sandwich?