The Mishnah (Taanis 26) teaches us “MiSheNichnas Av m’maatim b’simchah” – at the beginning of Av we should moderate our joy. Numerous disasters affected the Jewish people on Tish’ah B’Av, such as the destruction of the First and Second Holy Temples in Jerusalem. Our practices of mourning are increased as we enter the month of Av, and they become even more intensified in the week of Tish’ah B’Av.
There are several halachos that govern our daily lives as we enter this state of public mourning for the destruction of the two Batei Mikdash. Although there is a prohibition to learn most Torah material on Tish’ah B’Av, since Torah learning inherently brings one to simchah, and this would be a distraction from mourning the loss of the Beis HaMikdash, one may always say T’hilim for a sick person. For general recitation of T’hilim, there are several opinions. Some poskim discourage the recital of a lot of T’hilim on Tish’ah B’Av, others are more lenient after chatzos ha’yom, and others are more lenient for women.
The Kaf HaChayim (551:1) teaches that anyone who meticulously observes the halachos of the first ten days of Av, thereby demonstrating his personal mourning over the churban of Yerushalayim, will merit to witness miracles in time of Mashiach. May we all merit to see these miracles speedily and in our days.