A final interesting point explained by Rav Shmuel Eliyahu is the prohibition against eating meat during the nine days. The standard explanation is that the Rabbis have a statement, אין שמחה אלא בבשר ויין, real joy comes with wine and meat. This is why we are actually commanded to eat meat on the holidays in order to increase the joy we are supposed to feel at that time.
It would certainly make sense that refraining from eating meat decreases our happiness. This is appropriate during this period of mourning.
Rav Eliyahu offers a different explanation that meat represents קרבנות, the Temple sacrifices. In the desert, the only meat eaten had to be part of a קרבן. During the pilgrimage festivals, people offered a קרבן חגיגה, that allowed the contributor to take some of the meat of the sacrifice and eat it at home. This applied even to non-Kohanim.
The קרבן פסח had to be eaten by every Jew on Seder night and it involved the consumption of meat. Rav Eliyahu's point is that we should associate meat with the בית המקדש and קרבנות. By making such an association, our refraining from eating meat is directly connected to the loss of not having a Beit Hamikdash.
Therefore, when one agonizes the loss of eating meat during the nine days, he is really agonizing over the loss of Temple service and the קרבנות.