The Rav explained that an avel is enjoined from crying too much for his relative because, as the Rambam writes (Hilchot Avel 13:11), death is minhago shel olam; it is part of the natural course of events in this world. But the destruction of the Beit HaMikdash was an unnatural event. The Beit HaMikdash was much more than a physical structure. It symbolized the relationship between Hashem and the Jewish people. It was the focal point of spirituality in the world. When we mourn the loss of the Beit HaMikdash, we are not crying for the wood and the stones. We mourn the fact that we no longer see Hashem’s presence as clearly in the world and that our relationship with Him is strained. We long for the day when the Jewish people will reunite with Hashem and feel his closeness once again. In other words, we hope for the day when the world will return to its natural state. That is why we are obligated to cry on Tisha B’Av and there is no limit to our mourning because the loss of the Beit HaMikdash is a reality we can never come to terms with.
