In historical terms, Tisha B’Av – the 9th of the month of Av – was a multiple disaster.
It was the end point of a major war that we lost.
There was a huge massacre — and also the dispersion of the Jewish people to many countries.
It resulted in the loss of independence and of our ability to act as one, united people.
It signaled wholesale change in our way of life: religious, practical and economic.
These results have not diminished with time.
The lack of unity, the lack of common purpose, the loss of the feeling that we are one people: all these began about 2,000 years ago.
And they have not changed very much.
When one suffers an accident that leaves him maimed and handicapped, he may eventually forget the pain – but he will always remember that his face and his body are no longer the same, that his present life is different.
If there is something to mourn – these are the results of Tisha B’Av that should be mourned.
–Rabbi Adin Steinsaltz
From an essay, "Tisha B'Av: Why We Should Still Care," by Rabbi Adin Steinsaltz