I'd add that with enjoyable, low-effort time-killing activities, one may still have to be careful not to space out and wind up killing hours & hours on something that's fluff with diminishing returns, like Facebook or Twitter or channel surfing. (I try to consciously catch myself before I idly pull up a game of Solitaire or Freeciv or whatever, to check I'm not about to waste 10 minutes or 4 hours because my brain was in cruise control.)