A common thing that most diets will say is, "Eliminate junk foods and fast foods." The insinuation is almost that you are never to eat these foods ever again because they will make you fat and unhealthy. If you indulge, and eat some McDonalds or eat funnel cake at the fair, then somehow you are breaking the "rules" which almost always triggers the guilt feelings, or the feelings of "I'm not strong enough. I'm weak. I have no self control."
Now, it is true that junk foods and fast foods can contribute to things like weight gain and high cholesterol, however, there is a big difference between eating these foods all the time versus eating them on occasion. If your diet is Taco Bell on Monday, Burger King on Tuesday, Pizza Hut on Wednesday, and potato chips and soda for afternoon snacks, then yes, eating these empty calories loaded with fats, sugars, additives and preservatives will affect your health and weight. But if you have a Chalupa once every six months, or eat a Krispy Kreme donut at a work event a couple times a year, that occasional indulgence is not going to hurt or wreck all the effort you've put into creating a healthier you.
...The thing to remember is moderation...
Most of us in our daily lives have to go to social gatherings, work functions, community events, or parties, and food is typically the center of attraction, and the eating choices at these events are not always clean and healthy. Life is too short to not indulge once in awhile and enjoy some of these foods with others at special occasions. To say that you will never eat things like a donut, potato chips, or a fast food burger with fries ever again in your life is perfectionism thinking, and creates a very high and stressful standard for one to live by. It's more flexible and less stressful to say that you choose to eat healthier with the occasional indulgence versus saying, "I can't have it. I have to be strict about my food."
The thing to remember is moderation and quality of the food. For example, there is a difference between eating a handful of potato chips versus eating a whole bag of the chips. There's also a difference between eating organic potato chips versus eating potato chips loaded with additives and preservatives. And, there is a difference between eating potato chips once every 3 months or eating them every day. If you start cleaning up your eating by doing things like eating more fruits and vegetables, eating more organics, and drinking more water, then an indulgence here and there is not going to throw you off your path of healthy living.
In fact, you may find that because of all the cleaner eating you've been doing, when you do choose to have a junk food or fast food, eating that food now causes you to feel sick or the taste is not as delicious as you remember. The body adapts pretty quickly, and it will adapt to all of your healthy habits to the point where you naturally just stick to the better foods because it simply makes you feel better, and that starts to become far more important to you than anything; feeling terrific!