Huh, I quit for two years once, after smoking a fair bit daily for more than 15 years, and I gotta say, it wasn't hard at all. And I most definitely do have an addictive personality, addictions run all through my family. I didn't even mean to quit pot, but the months just kept rolling by until suddenly, it'd been two years.
Alcohol and cigs, being physically addictive, I've had probs with those. I drink very rarely now, as too many people in my family died from it, including my mother, with me in the car when she hit a telephone pole doing 60 in a Pinto. Still smoke cigs, haven't been able to shake that one. But pot? Never really noticed any withdrawal effects, and certainly not any physical ones.