Let me show you an example, perhaps through this example, you can see what I'm talking about.
Let's say you're walking along, minding your own business and suddenly you see an ad on the screen of a cupcake. You suddenly get an urge for a cupcake by seeing an ad for a cupcake. You sit back and realize that you're not really craving for a cupcake, you're only craving for it because you seen it. Thus, there is no need to eat a cupcake to satisfy your hunger.
Let's say you're at home, and grandma baked you a cupcake. You ask yourself, "Man, I really love grandma's cupcake, and I'm really craving for one, so I'm going to eat one." You eat one, think it's the best thing ever, and you forget about it and enjoy your time with grandma.
Now, let's say you're on your "diet" and you're confronted with a cupcake. You say to yourself, "I really want a cupcake, badly. But since I'm on my diet, I can't eat it. I don't want it." You go do something, but your mind is still on that cupcake. You tell yourself, "No, I'll just eat something else." You do. That cupcake is still on your mind. You drink some water. The cupcake is still on your mind. Finally, instead of having one cupcake, you have five cupcakes and you sit by yourself feeling guilt and anger.