What feels obvious can still deserve verification.

Obviousness is a feeling, produced by familiarity, repetition, and how easily something fits with what you already believe. It is generated inside you rather than delivered by the fact itself, which is why so many obvious things turn out to be wrong. The things nobody checks are precisely the things nobody has checked.

Pick one assumption underpinning something important and actually verify it. The date, the number, the thing everyone knows about how this works. It feels faintly ridiculous to check, and it occasionally saves an enormous amount of misdirected effort.