Are there single serving portions of certain foods that you can never seem to finish?

For example, I can never finish a whole box of raisins, or an entire packet of oatmeal. I can’t eat two whole eggs, either. I know that none of those things are a large amount of food, but for whatever reason I can’t ever seem to finish a serving of any of them.
Is that really odd, or are there certain foods that you can’t seem to eat very much of before you can’t take another bite?