Русско-английский словарь пословиц и поговорок
ПАСТУХУ ДРЕМАТЬ, ТАК СТАДА НЕ ВИДАТЬ
When a man neglects his duties, he finds himself in trouble
Cf:Careless shepherds make many a feast for the wolf (Am.,Br.). A careless watch invites the vigilant foe (Am.). Wolves rend sheep when the shepherds fail (Br.)