I've seen many articles that people will habitually underestimate the amount of food they eat and overestimate the quality of the food they eat without realizing it.
If this sounds nuts to you, keep a food diary for a week. You will be blown away as I was. You might be especially surprised how many calories are in bagels, fruit juice, and pasta.
This article on the BBC illustrates this point:
BBC - Science & Nature - Metabolism and Weight
I also like this site that has pictures of what 200 calories looks like in various servings of food. Be sure to click on the picture to see the size of the serving in perspective:
What Does 200 Calories Look Like?