Waiting for Moshiach on Tisha B'Av
Once, before Tisha B'Av, the Galanta Rav was sitting with his talmidim on the porch, waiting to daven Maariv. After a while a young talmid approached and said that three stars were already visible, so they could begin.
The Rebbe replied gravely, "Let us wait a few more moments. Maybe Moshiach will come and we will not have to say Kinos this year."