Tonight starts the saddest day in Jewish history. The 9Th of the Jewish month Av. This is the day when the Holy Temple was destroyed. Even now we mourn it’s destruction. We will fast starting tonight and until Sundown tomorrow. A strict Jewish fast means no food or drink is taken. There are various exceptions to it, but one should consult his local Orthodox Rabbi about them because they differ according to personal circumstances.
Aside from the physical aspect of the fast there is also a spiritual one too. We are grieving for the destruction of the Temple as if it happens today.
At the same time it is a day of hope. Even when we are crying about the Temple that is lost, we are praying for the Temple that will be rebuild. We know it will happen. And we hope that this moment is at hand.
May all, who will fast have an easy fast and may the Beis HaMikdash be speedily rebuild.