The upcoming month of Ab (begins August 1st) is known as a time of mourning, because of the events that took place on the first days of the month. Specifically, the destruction of the first Bet haMikdash, the Holy Temple of Jerusalem in the year 586 BCE and of the second Bet-haMikdash in the year 68 ACE. Both Temples were destroyed on the dame date: the 9th of Ab.
Even thought we concentrate our mourning for the Bet haMikdash on the 9th of Ab and a few days before that, our rabbis mentioned a few traditions to be kept year-round to remember the destruction of our Temple (zekher lachurban).
The best known of these customs is that the groom breaks a glass at the end of the wedding ceremony and says: Im eshkakhech Yerushalaim ... "If I ever forget you Yerushalaim, may my right hand wither... If I won't remember Yerushalaim in the happiest moment of my life". The rabbis also mentioned the custom that on the day of his wedding, the groom places ashes in his head, in the place where he usually wears his Tefillin.
Another tradition which is widely observed is that at the entrance of a Jewish home, close to the main door, we leave an unfinished unpainted square on the wall. Symbolically, it is as if we were saying: ...How would I dare to have a complete beautiful house, while the House of God is still in ruins...
For the other traditions zekher lachurban see HERE (Maimonides, Ta'aniot, 5, 12-15).
Click HERE to learn the HAFTARA for Shabbat Chazon, (the Shabbat previous to 9 BeAb).
See HERE BIBLICAL ARCHEOLOGY: "The city of David on Capitol Hill".