[archduck]

This calls to mind Csikszentmihalyi’s concept of _flow_. There’s too much of it to go into here, but this page illustrates how it happens and what it's like: https://en.wikipedia.org/wiki/Flow_(psychology)

I posit that any activity which falls short of flow state will also cause energy drainage in kind. What distinguishes introverts and extraverts in a given social interaction, then, has to do with the degree to which they consider themselves challenged and how skillfully they think they are performing. High challenge + high ability = flow, which is an energizing state where you lose track of time. Mess with those parameters a bit and you get boredom and anxiety (along with shades of other things), which are draining states different in kind.