After nearly a month of fierce fighting inside Jerusalem (see "Today in Jewish History" for Tammuz 9), the armies of King Nebuchadnezzar of Babylonia broke through into the Temple compound, where they feasted and vandalized until the afternoon of Av 9, when they set the Holy Temple aflame.
Links: The Destruction of the Holy Temple
During the “Nine Days" from Av 1st to the Ninth of Av, we mourn the destruction of the Holy Temple. We abstain from meat and wine, music, haircutting, bathing for pleasure, and other joyous (and dangerous) activities. (The particular mourning customs vary from community to community, so consult a competent halachic authority for details.)
Consumption of meat and wine is permitted on Shabbat, or at a seudat mitzvah (obligatory festive meal celebrating the fulfillment of certain mitzvot) such as a brit (circumcision), or a siyum celebrating the completion of a course of Torah study (i.e., a complete Talmudic tractate). The Lubavitcher Rebbe, of righteous memory initiated the custom of conducting or participating in a siyum on each of the Nine Days (even if one does not avail oneself of the dispensation to eat meat).
Citing the verse "Zion shall be redeemed with mishpat [Torah] and its returnees with tzedakah," (Isaiah 1:27) the Rebbe urged that we increase in Torah study (particularly the study of the laws of the Holy Temple) and charity during this period.
Links:
Nine Days laws and customs
Daily live siyum broadcasts
Learn about the Holy Temple in Jerusalem
On Yom Kippur, we are all in recovery.
Recovery of our true selves.
Look beneath the stormy waves of life, beyond the failures, the guilt, and the pride.
Beneath the surface dwells a calm, pure soul that only desires to fulfill the divine purpose for which it came to this place. To run to do a mitzvah. To absorb the wisdom of Torah. To find an infinite G‑d in all you do upon this earth.
Embrace that essence. Return to it.
Recover that which is truly yours.