油断大敵: there's many a slip twixt cup and lip, carelessness is what will get you into trouble; security is the greatest enemy; Idleness is the devil's workshop

unpreparedness is the greatest enemy

the previous day; the day before

油断: negligence

油断: to be negligent

being unprepared

(Classical Japanese, archaic) entrust, leave / (Classical Japanese, archaic) abandon oneself to / (Classical Japanese, archaic) devote oneself to

play / game

examination, exam, test / quiz

to go; to come to one's place / to (a letter) be delivered / to depart / to rely (on a method) / (年が～) to age / (うまく～) to go well / イく: (slang) to have an orgasm, to come, to cum