If you play an MMO long enough, you get to the point you can not play the actual game, and anywhere you are, you can be playing in your head, releasing those endorphins you have conditioned yourself to get.
Helpful tip if you're facing jail time. All the other prisoners will wonder why you are so happy sitting in your bunk smiling for hours and hours on end. Works good for annoying family gatherings, but gets annoying when it becomes involuntary, such as on nice vacations, honeymoons, etc.
Indeed, at advanced levels, the actual game can become less pleasurable, as you don't have the LFG delays and such when playing in your head, much like remembering the good times with an ex gives you rose-colored glasses.
The small price you pay for this is real world endorphin releasers becoming much less effective. Romantic partners become annoying distractions from the game - 'Sex of Duty 4'. Pets the same, like a Sims add-on requiring maintenance. Housework 'needs' have the 'need' line redrawn to 'is law enforcement concerned?'