My guess is that this person is very ill/nauseated/in bodily discomfort, and then either couldn't eat their breakfast or 'rejected it.'

Hi Joseph. I am little puzzled by this as it is not possible to see all of the original text that you have posted. In the paragraph you have quoted, 'breakfast' only needs to be the usual meaning of the meal that we eat shortly after getting up in a morning. When someone is sick, they may not be able to eat breakfast. I am unsure about why you ask about the season of Lent, but Christians often did not eat breakfast before they received Communion. In a similar way, it is possible that some people may have also not eaten breakfast during Lent as a way of going without food. Christians often practice 'fasting', or going without food, during the period of Lent.