Today is the 5th day of Av, Erev Shabbat Chazon
On Tisha BeAv (begins Monday July 19th at night) , the national Jewish day of mourning, we behave almost as mourners do.
All these restrictions actually help us to feel and internalize sadness and grief as if our Bet haMikdash was destroyed 'yesterday'.
WORK: That is why on Tisha BeAv it is not recommended to work. The reason for avoiding work is not the same as for Shabbbat or Yom Tov but because working will divert our minds from the mood/feeling of grief. Refraining from work on Tisha BeAv is not an established prohibition, but ultimately depends on one's family tradition.
LIMUD TORAH: On Tisha BeAv We don't study Torah, because studying Torah is considered an activity which triggers happiness. We can read and study, however, books or texts with a suitable 'sad' content such as the book of Iyov or Ekha, etc.
TEFILIN: We do not use Tefilin in the morning, same way as a mourner proceeds during the first day of his Abelut. We do use Talit and Tefilin for Mincha.
In Yerushalaim the Sepharadic Minhag is to wear Talit and Tefilin privately, before one goes to the Synagogue and say the Shema Israel at home with Talit and Tefilin.
SHE-ELAT SHALOM: We don't greet each other as usual, because our mood should be a mourner's mood.
Our Chakhamim assured us that those who cry for Yerushalaim will have the merit to rejoice with Yerushalaim, seeing BH soon, the reconstruction of our Bet haMikdash.
Shabbat Shalom from Yerushalaim!!!