I sit down in the morning and plan the whole day of eating. I decide if I can eat what the family is eating for dinner or I need to make something just for me.
I do something similar; I eat pretty much the same thing for breakfast every morning (just different flavors of yogurt and different varieties of Kashi cereal), so I know that breakfast is taken care of, easy peasy, no worries. Then I decide before lunchtime how the rest of the day is going to go. Do I want to splurge a little bit on lunch, and have a slimmer dinner? Or do I want to have a smaller lunch and have a bigger dinner with my family in the evening? Some days it depends on what the rest of the day holds (will hubby be home for dinner, or is it just the kids and me? Can we go to lunch with friends?), while other days, it is more about what ingredients I have on hand for either meal. So I try to balance it out then, early in the day, and that helps determine what I can snack on in the afternoon.