I've been on the Food Doctor Diet recently, and I've tried two ways to cut down on my chocolate: 1) only eat Fairtrade chocolate, which cuts out most of the easier temptations! and 2) only eat a small amount. (I can't yet make it only super-dark plain chocolate as he suggests). I've managed to cut it down to 1/2 a bar at a time of the Co-op Fairtrade milk chocolate, about 1-2 times a week (I'm amazed at that even as I 'm typing it)
But I've never yet been able to eat one chunk and leave the rest