Most diets are actually pretty flexible and allow us to eat certain things that we might be better off cutting out completely.
For example, some diets allow a couple squares of dark chocolate. If you can eat 2 squares of chocolate and then stop, that's fine. But for most overweight people, this is just not possible.
Another cause of many slip ups is alcohol. For those who are used to drinking a lot, it is hard to stop after one beer or one glass of wine. And even if you can do that without difficulty, alcohol lowers the boundaries of self control so that it becomes harder to say no to the unhealthy snacks that are often served up with a drink.
Most people have 'trigger foods' that they cannot eat just a little of. Often, these trigger foods will set off a binge of eating all kinds of other forbidden foods too.
Common triggers include chocolate, cheese, bread, pasta, nuts, chips, certain fruits, salty food, or sugar. Make your own list and make it as specific as possible. For example if cheese is a trigger for you, specify different cheeses. If it's chocolate or candy, write down the brands.
Then put your list into order. Like Colette with her truffles, it is best to cut out all of your triggers completely at first. But as you approach your goal, you can begin to add them back.
When you add them, begin with the specific recipe or brand that you can handle most easily. That way, your confidence will gradually grow until you find that you can handle just about any food without bingeing.