A proverb meaning 'don't let your guard down' — a warning that carelessness can lead to danger or mistakes.
怪我が治っても、完全に回復するまでは油断は禁物だ。
Even if the injury has healed, you must not lower your guard until you're fully recovered.
試験直前だからこそ油断は禁物だ。最後までしっかり復習しよう。
Especially right before the exam, don't be careless. Let's review thoroughly until the end.
山道は天気が良くても油断は禁物だ。急な崩落があるかもしれない。
On mountain trails you shouldn't be careless even in good weather; there might be sudden rockfalls.