The Talmud makes an apparently surprising statement when it says (tractate Taanit, 26b), "There were never such wonderful days for Israel as the 15th of Av (Tu B'Av) and Yom Kippur." The 15th of Av is nicknamed "Love Day" in Israel, for it's the day when matches were traditionally made, as described in the above-cited Gemora. Several questions arise: First, what does Yom Kippur have to do with "Love Day"? Second, many people dread the fast and the ax of judgment hovering over their necks on Yom Kippur, so why would it be described as one of the two most wonderful days for Israel?
Our Talmudic sages reveal their divinely-instilled wisdom by juxtaposing Tu B'Av and Yom Kippur. Yom Kippur is also a "love day", when Hashem demonstrates his limitless love for His chosen people. For the mere price of a 25-hour fast and saying we're sorry, Hashem forgives us of all of our wrongdoings against Him. Important - Yom Kippur does not atone for the sins of man against fellow man!!
Imagine that your national government declared a retroactive annual moratorium on all tax violations and unpaid debts once a year, as long as you appear in federal court, apologize in public, and fast for the day. What a deal! A wild dream? In Judaism, it's a reality. When we fast, beg Hashem's forgiveness, and promise to try our best this coming year, Hashem wipes our debt slates clean! A wonderful day, or not?
Gmar Chatima Tova!