Yeah I have. I've been smoking green almost everyday sine I was 12, I'm 21 now, not smoked for 3weeks and this is the longest I've managed.
It definitely does take a hold of people, I know lots of people who maybe won't admit it does but at the same time they go mental when there's none about.
I suggest a change of scenary for a week or so, if you can get away, to kick start the process. It's much easier then. Try fill up your day if you can't get away, the more distracted you are the better.
When you stop don't expect to sleep for a week or so and also expect to sweat quite a bit aswell as the mental stuff. It's not pleasant but I think it's worth it.

Goodluck! xx