I've "given up" on WoW about 3 times now, and after some time away I go back. Right now I'm in a time away phase. So cancel your account, but keep the software installed on your computer. A time will probably come when you want to go back and play some more. It really is a well-made game, and a bunch of fun.
And by the way, I've learned not to focus on levels. Just enjoy the questing, the plot lines and process. The levels will come. If you get bored with that, just level a toon to a "9" level (19, 29, 39) and spend some time in the battlegrounds. A typical bg battle lasts about 20-30 minutes, which isn't bad, and you get to fight real other players, rather than the NPCs you usually fight on quests. I've had a lot of fun just doing bgs.
Final thought. I've actually met some pretty nice friends online in my guilds. So join a guild, and not only do you meet cool people to chat with while you play, but they can help you with some of the harder quests, getting good gear, etc.
Have fun!
Peace