In AN 6.19, the Buddha tells monks that mindfulness of death for one in and out breath or while eating one morsel of food is better than mindfulness for a day or a day and night. The exact words were:
‘When this was said, the Blessed One addressed the monks. "Whoever develops mindfulness of death, thinking, ‘O, that I might live for a day & night… for a day… for the interval that it takes to eat a meal… for the interval that it takes to swallow having chewed up four morsels of food, that I might attend to the Blessed One’s instructions. I would have accomplished a great deal’ — they are said to dwell heedlessly. They develop mindfulness of death slowly for the sake of ending the effluents.
"But whoever develops mindfulness of death, thinking, ‘O, that I might live for the interval that it takes to swallow having chewed up one morsel of food… for the interval that it takes to breathe out after breathing in, or to breathe in after breathing out, that I might attend to the Blessed One’s instructions. I would have accomplished a great deal’ — they are said to dwell heedfully. They develop mindfulness of death acutely for the sake of ending the effluents.”
Is the reason for that the “imminence of death,” that for instance one moment before death is more perilous than expecting death in a day? So therefore it’s more urgent and earnest?
I have another idea of why it’s better. Although intuitively doing something good for a day is better than doing it for a second, there is also the idea of being in the moment.
For example, thinking ahead or behind for a day in general is not the immediacy of “now.” In the same way Zen masters instruct, “be here now” perhaps being mindful of death and impermanence in the direct immediate is superior to, “just for today,” because even looking ahead half a day is not “in the now.”
Is this correct?