Dhammānussati: Recollection of the Teaching
One of the standing recollections, bringing the teaching deliberately back to mind. A church with a name for being alive had received and heard something once and let it go cold, so the first move is backward: retrace your steps to where you last had it. A teaching does not keep itself; it stays alive only by being taken out and gone over again.
Sati: Mindfulness
Sati is remembering, holding something in mind as the moment happens. "Keep it" and "watch" ask for the same thing, the teaching kept close enough to hand that it is there when the hour arrives. A night watchman's whole worth is being awake at the one hour that turns out to matter, and every other waking hour is the price of that one.
Appamāda: Heedfulness
Heedfulness is diligence that stays on the job. Nobody decides to let the house go dark; attention just drifts, and Sardis kept its reputation for being alive long after the life had gone out of it. "If you won't watch" carries the same weight as the Buddha's last words, which were to keep at it with heedfulness.
Maraṇassati: Mindfulness of Death
Keeping death in view as certain and its hour as unknown. The thief's whole advantage is timing: no word sent ahead, and no one sets an alarm for the night of the break-in. Held this way, the unknown hour becomes plain practical advice, since the one who expects it at any hour is the one found ready.
Saṁvega: Urgency
Saṁvega is the jolt of seeing your situation as it stands, with the push to act on it. "Repent" is the turn that jolt produces: see the fault as a fault, own it, and change course while there is still an hour left to use. Waking to the smell of smoke gets you out of bed, and that is worth more than a calm night of sleeping through it.