Because of a scheduled power outage, my hubby and I decided to go out for breakfast. As normal, I could not finish my meal and asked for a container. (I know, if I cared about the environment, I would have had one of my boxes in my purse.) The container they gave me had about the same proportions as my lunch boxes, but it was easily twice as large. As I was scooping the remains of my meal into it, I realized that it was actually getting full! That one meal is enough to serve me 3 times, maybe 4.
I had a vague sense of serving size vs meal size, and how my stomach can only hold a little more than a proper serving of food. It was just learning volumetric calorie estimation and then seeing a restaurant meal try to fit into that format that drove the point home.