I took a break from WoW for about 1.5 years, once everyone started hitting the level of doing 40-man MC raids and such. The time investments were getting to be too much (6-7 hours in an afternoon?!), and found myself staying up later and later every night. Once it started impacting work (due to getting up later or being sleepy all day), I quit cold turkey.

I'm back, but the whole experience gave me a whole new outlook on the game. I'm not reluctant to just step away for a while now if necessary. Boxing gives me a little of that latitude to play birefly and walk away. No commitments to others to have to be around. I'm getting a bit more into the raiding again, but I'm trying to keep it pretty light. Just a 10-man Naxx a week (5-6 hours total), on top of a nightly heroic or two.

If the game is impacting the rest of your life, just walk away from the game for about a month. Just set some priorities.