Like everything else in life, one has to exert self control.
There are worse stories I've heard about people getting addicted to games, personally I know someone who was so addicted he had to repeat first year university (WE all know its not his smarts, he got into university on a top scholarship!)
I'll admit I've spent whole days at a time playing , but when there are more important things in life that requires your attention, well, then you stop. I stopped playing for four months coz of multiple reasons, just played again couple of nights ago for a few hours.
Its all in the person, not the game.
And if anyone else is on horde side, twisting nether and want to quest sometime look me up-> trohu (50 Tro Hunter) or Tadru (30 druid)