I was in the same position as you last summer and I managed to successfuly quit (and then come back because situations changed)
The best advice I can give is to find something else to fill your time, a hobby. Sports are good because usually that means you're interacting with other people and keeping healthy although picking up a musical instrument / painting / writing whatever it is, even just reading a book. When you would usually log onto WoW just do that other thing instead and eventually you'll forget about WoW or be able to control your playtime consciously.