On the eve of Rosh Hashanah, Rav Yisrael Salanter would instruct each member of the family how to behave.  He would warn them against getting angry and against idle conversation, for they were all in grave danger.  Their carefulness was to last at least through the morning when the judgement is strictest.

From Sparks of Mussar by R Chaim Ephraim Zaitchik