Resentment in flow

Flow is addictive, as well as flow can be suboptimal inasmuch as it carries resentment as a background emotion. This is evident in the way flow is defined in terms of “balance” of certain factors; tasks characterized to be too “easy” or “chore-y” apparently cannot enable a flow-like experience because, according to this definition, we generally resent doing them, and would rather be doing something else (“in the zone”).

Open question: What is the nature of this resentment? Can a flow-like experience (if not flow itself) be maintained regardless of the specifics of one’s doings?