I look at my healthy eating habits as a committed lifestyle change. The only thing that has worked for me is thinking of certain foods from an addiction perspective. Just as an alcoholic in recovery can't have a sip of alcohol, I believe certain foods are addicting to me, & therefore, I can't have them. Once I put a bite of those addicting foods into my mouth, it triggers my desire for more & I go into a downward spiral. Just "say no" and eat only foods that you know won't trigger a craving.
It is hard to live this lifestyle at first, but once you commit to it, it becomes a part of who you are. It has helped me immensely and has virtually eliminated my cravings for processed foods & sweets. Just make sure you are getting all of your calories & nutrients from foods in your meal plan!