I think what's important is to consider the difficulty of making these choices, and to set up your environment so that it's easier to make the right choice.

I've lost weight and kept it off by making sure I don't have sweets and other types of food that I know I'll down in ten minutes. But if I don't have any on hand, I won't eat any.

Ditto for normal food: if I increase the portion of filling, low-calorie foods (think salads and other greens), with a lot of protein, I know I won't have cravings later in the day and feel full longer. But if I buy fatty sausage, with a hefty helping of salty cheese, I'll eat until I explode.

If when I'm hungry I have a choice between "a quick bite" of something very palatable, calorie-rich but nutritionally poor, and a "good" meal, I know I'll make the wrong choice. But if my only choice is the good meal, I'll eat that and stay on track.

This also has a positive feedback effect: after a while, not only did I stop craving various junk foods, but they actually don't register as food anymore when I see them in ads or similar. Which, of course, makes it easier to stick to the "diet". Now, when I'm hungry, I crave "actual" food. The other day I couldn't have lunch on time, and all I could think of was a fat bowl of lettuce with some roasted chicken breast and yogurt. Walking in front of the local McDonald's peddling their latest mystery burger didn't do anything to me.