This isn't really the same but I just quit smoking cigarettes...it's been about 2 weeks and I haven't smoked anything since. I started smoking little cigars instead of cigarettes, not inhaling as much. I tried quitting cold turkey but my will power is pathetic. 2 weeks and I haven't smoked once.
maybe I'm wierd, but I don't ever feel a dependency on weed and alcohol. I used to smoke every day, drink 4 or 5 nights a week, getting plastered...but I just changed my surroundings and that was that.
but seriously, your last celebratory indulgence will not be your last. I used to do that shit all the time with cigarettes, "yeah, this is my last one, promise." never worked. be careful.