If you want to successfully lose weight and keep it off, you have to lose the "good food/bad food" mentality. Truthfully, there are no foods so bad, in terms of weight loss, not health, that you should never eat them.
One reason is that it sets you up for a binge. You keep saying "no" to something you really, really like. Eventually, you'll start craving that food. And when you finally give in, you'll eat too much of it. If you'd allowed yourself small quantities of it along the way, you would most likely avoid the binge.
Another reason is what guilt does to your efforts. When you say something's "bad" and you're never going to eat it again, you set yourself up for a guilt trip if you do. You feel bad because you didn't stick to your plan. You start a cycle of beating up on yourself. And sometimes, you talk yourself into a binge because you've already blown it by eating this bad food.
What you have to do is learn the art of the trade-off. I'm most familiar with Weight Watchers and the point system, so I'll use it as an example. You can use whatever you're counting--calories, fat grams, etc. the same way. Let's say I really want the real deal--Buttermilk Fried Chicken. A lot of the traditional side dishes have a lot of fat and calories. Mashed Potatoes and Gravy. Biscuits. And a meal like that is often topped off with a nice big slab of apple pie a la mode. (No, I'm not trying to make you all hungry. But I can't make my point without food examples. lol)
To do the tradeoff, I look at that menu and ask, "Which foods can I reduce the points in?" The mashed potatoes and gravy are easy to make low points. I really want the real fried chicken, so I limit myself to one piece, rather than make any of the reduced point recipes I have. I skip the biscuits. You cannot make biscuits low points and have them still taste good. I add vegetables and salad. I substitute an apple streusel for the pie. Most of the points for the pie are in the crust, so by substituting a streusel topping, and eating a very small portion, I can eat dessert. I skip the ice cream. If my day is super point heavy, I make a plain baked apple with cinnamon and a bit of sugar or maple syrup.
You don't have to make the same tradeoff each time, either. Next time, I may really want the pie and ice cream. So I make a reduced point chicken recipe. If I want the biscuits, again, I do reduced point chicken and dessert recipes.
The point is that you can eat what you want, just not every day. Not every meal. You have to make choices. If I have a day where I'm feeling rebellious and want it all, I remind myself that I can plan to eat some of it next week. Or tomorrow. It's much easier to stick to a food plan if you ask the positive question--how can I eat what I want? And work with it.
I know some people have what are called "red light" foods. They swear they cannot stop eating them once they start. I don't know about the validity of that. I really think that you can learn to eat them in small portions. First, never have them in the house. Eat them in restaurants until you can eat the right portion size. Then you can bring them into the house, but immediately portion them into single-serving packages. Plan when you're going to eat that package. Sit down with it and savor every bite. Then, if you're tempted to get another package, go for a walk. You won't be perfect as you try to beat the red light food thing, but you will make progress and can learn to deal with them. You just have to let go of the idea that these foods have some special power over you. They don't. They're just food. And learning to deal with food as "just food" is crucial to winning the whole war.
Good luck, everyone. :)