“Each day, therefore, should be arranged as if it were the last: not as if it were the last, but as if it could be the last.”Seneca · Scrisori către Luciliu · 65 · Scrisoarea 101
The nuance matters: do not live in permanent panic, but keep in mind that nothing is guaranteed. The practical effect is twofold. First, you stop postponing what matters, because "later" is not assured. Second, small annoyances lose their grip, since they look absurd against a day that might be the last. A parent's phone number untouched for years is exactly the kind of deferral this thought removes.
Why it matters For anyone postponing calls, apologies, or projects: memento mori works as a priority filter, not as a fear.