Once R’ Yaakov Kamenetsky zt”l was to meet someone at Manhattan’s Penn Station at 7:00 A.M. for a trip out of town.  R’ Yaakov arrived at the station looking exhausted, having spent a sleepless night.  He explained to his companion that when he had gone to set his alarm clock before retiring for the night, he remembered that his gentile neighbor worked the night shift and would have just gone to sleep at the time that the alarm clock was set to go off.  It was hot summer night when everyone slept with their windows open and the neighbor would quite possibly be awakened by the alarm.  Therefore, R’ Yaakov did not set the clock; instead, he stayed up all night learning to make sure that he would be on time for his early departure. ~ 5 Great Lives