Most observant Jews fast on the 9th of Av (see here for more info). I do not fast; we do mark the 9th of Av in our own way as a family. For myself, however, Tisha b’Av (next Thursday) is usually marked by me looking at the calendar and freaking out that I have only about 6 1/2 more weeks until Rosh Hashanah and OH-MY-GOD-I-HAVEN’T-EVEN-BEGUN-MY-COOKING-AND-LOOK-AT-THE-HOUSE-IT’S-A-DISASTER-AND-OH-LORD-WHO-DID-I-LEAVE-OFF-THE-CARD-LIST-BY-MISTAKE-LAST-YEAR????????
A heartfelt way to mark the destruction of the first and second Temples, I think.