I think like any other addictive substance, you have to expect some sort of withdrawal from processed foods. Your body needs to adjust to the different levels of sugar, carbs, nutrients as you begin to eat more naturally. There are plenty of good substitutes for junk foods- things like kale chips, or flaxseed crackers. You can make homemade mayonnaise using silken tofu and a food processor, or just replace it with ripe avocado.

Eating a balanced diet of protein, carb, and fat is important too, and will affect your cravings. Eating upwards of 30-40 grams of fiber a day (high fiber oats, chia seeds, oat brand, that kind of stuff) will keep you satisfied longer, and can be just as tasty as an empty-calorie snack that leaves you hungry ten minutes later. Self control is also integral; unfortunately you're going to have cravings and its ultimately up to you to have one piece of chocolate and no the entire package! Personally, I don't buy crackers at all because I will eat them in one sitting. That isn't to say that, once in a while, if you go overboard that you're a failure- not at all! Just make sure that you stay disciplined and give yourself a nice treat once in a while. Some people write down everything they consume every in order to keep things straight.

Good luck to you all!