The Gemara (Chagiga 5a) tells us, "Rebbi was holding a sefer Eichah and reading from it. When he reached the pasuk, 'He threw the glory of Yisrael down from the heavens to the earth" the sefer fell from his hands and he exclaimed, '[Bnei Yisrael were hurled] from a tall roof to a deep pit.'" The pasuk already told us that Bnei Yisrael were thrown down from the heavens to the earth; what was Rebbi adding when he exclaimed that they were cast into a deep pit?
Rav Wolbe (Da'as Shlomo) explains that we have a basic misconception with regard to the Churban. We perceive the mourning associated with the Churban specifically in regard to the destruction of the Bais Hamikdosh, the holiest site on earth. While the destruction of this hallowed abode was an enormous tragedy, it is not the only aspect we mourn on Tisha B'Av.
When the Bais Hamikdosh stood, the Jewish Nation lived a "heavenly" existence. Their entire lives revolved around spirituality. Ruach Hakodesh abounded and the simplest Jew lived and breathed ruchniyus and constantly strived to attain higher levels in this area. Their actions were a constant display of kavod Shamayim. It is quite probable that even the non-Jews lived on an altogether different level.
When the Bais Hamikdosh was destroyed, we did not merely lose a holy building; our entire world drastically changed for the worse. The Jewish People were cast from their heavenly existence down to the ground. However, Rebbi felt that Bnei YIsrael did not land on the ground. They fell into a deep pit devoid of any spiritual light and air. The physical world became the focus of attention, and with its great allure it draws people in - hook, line and sinker. Money and honor became the name of the game. Bnei Yisrael had landed in a deep pit. This pain is compounded with the pain felt by the Shechina being sent into galus. This is the tragedy that we mourn on Tisha B'Av.
Rav Wolbe adds a timely idea connected to the above pasuk. Rashi explains that after Hashem raised Bnei Yisrael to the highest heights of the heavens, he threw them down in one swift motion and not little by little. The Medrash adds that while the climb up was an arduous journey, the tumble down happened in a split second. When middas hadin (strict judgment) strikes, it strikes suddenly without warning. However, we find the same idea regarding the geulah, as the pasuk states (Malachi 3, 1), "Suddenly the Master whom you are awaiting will enter His Sanctuary" with the arrival of Moshiach. [May we merit his speedy arrival!]
Additionally, says Rav Wolbe, we find that Hashem often tests a person by seeing how they react when suddenly placed in a specific situation. The Medrash tells us that Kayin, Bilam, and Chizkiyahu all failed to properly answer Hashem when He appeared to them without warning. Had they had time to think about their response they certainly would have answered differently, but the litmus test to determine a person's level of spirituality is how he reacts when suddenly faced with a test. Preparation in advance arms a person for all scenarios. The summer months often come along with various situations that arise during vacation. One should prepare himself before embarking on his vacation lest he lose his bearings when faced with scenarios that might compromise his normal level of observance.