You can sit down for a half-hour to knock out a bounty or whatever and feel like you accomplished something, or you can play for hours and then just... stop for a bit between missions without feeling like you need to complete a plot element or reach some progression goal.
This is why it's been easier for me with my sporadic work schedule and interruptions to play Destiny than Wildstar. It's been nice to only play for 20-30 minutes and actually feel like I've progressed, even if only a little.