The first day
Today is only about getting to tonight. You do not have to understand what happened, decide what it means or feel any particular way. Grief after a breakup often arrives as a body problem first: no appetite, a racing chest, a stomach that will not settle. That is not weakness. It is your nervous system reacting to a loss, and it does not need your permission.
Today’s small step
Drink a full glass of water and eat something small, even if it is only toast.