A first step toward diet health is attention. Become aware of everything you put in your mouth. What is the consistency, the taste, the texture? How would you describe it to someone unfamiliar with it? Until eating with attention becomes habit, you could write your food (and drink, even water) in a special diary or notebook, along with your impressions and observations about it. The vast majority of people find that careful and consistent attention to their food and drink will bring better order and moderation in eating and drinking.
A second step, after beginning to be aware of your food and drink, is to notice the triggers to consumption. Many eat when anxious, for example. With practice you can learn better ways to manage your nervousness and fear, such as brief, focused meditation or even skillful breathing.