Well, Mihaly Csikszentmihalyi thought people were happiest in a state of what he called "flow". He defined flow as a "state of concentration or complete absorption with the activity at hand and the situation." In his book "Flow: The Psychology of Optimal Experience" he actually goes into depth about flow and how it explains the work paradox. Work provides a platform for people to dedicate their focus and achieve flow. At home, flow states are rarely achieved because leisure is often comprised of activities that don't require much attention or focus. This would explain why people complain about work all the time but have poorer moods and are more anxious during leisure time. Personally, I feel that the response to the work paradox shouldn't be believing that work is absolutely necessary in order to be content. I think it just means we should pay much more attention to how we spend our leisure time.