I am my first priority.

A person looking after everyone else, who has stopped eating properly and hasn't slept, eventually becomes a second problem for the people they're looking after. That isn't a moral argument. It's arithmetic.

First is about sequence, not importance. It means the sleep and the appointment go into the calendar before the calendar fills, because everything else expands to take whatever is left over.

Anyone who has tried it the other way round knows the ending: nothing left, and a slow resentment towards people who never asked for that much in the first place.