I think the advice about eating enough on the days before a long ride is very sage. This summer, I mistakenly tried to ride on days when I had had not eaten very big meals. Although these were not long rides, it was very hot and I was riding a lot more consecutive days in a row. It just doesn't work for me unless I pay very close attention to how hungry I feel. And this often means that I eat a Luna Bar as soon as I start riding, even though I have had a good breakfast.
It's hard to do this when everyone around me doesn't need to eat as much as I do!