During all the years that Israel was in the wilderness, on the eve of every ninth of Av, Moses sent a herald throughout the camp to proclaim, “Go out and dig graves, go out and dig graves!” and the people went out and dug graves, in which they spent the night. In the morning, the herald went and announced, “Let those who are alive separate from the dead!” The living then stood up and found themselves some fifteen thousand short [NOTE: One-fortieth of the adults died each year — see parashat Shelach-Lecha for narrative explanation]….In the last of the forty years, they did the same….finally when they saw that not one of them had died, they said: It appears that the Holy One has removed the harsh decree from over us. The declared that day a festival.
–Bialik and Ravnitzky,* 99:123
Perhaps if we considered ourselves “dead” each Tisha B’av [ninth of the month of Av] pending some extraordinary changes in our world — not so far-fetched as destruction of our environment, wars and hatred abound — we would use the day of mourning differently.
See also “Mourning Hope” at Clergy Beyond Borders news blog.
* See Source Materials for full citation, etc.
"A Song Every Day" 
Why is the kiddush levana said after ma’ariv at the end of Tisha b’Av? Is it because this blessing for the new moon could not be said at the usual time, when the month of Av began, because of mourning restrictions related to the nine days and/or three weeks preceding Tisha b’Av?
Saw this instruction about the kiddush levans in the Koren siddur, along with a lot of other rules about differences in prayers for Tisha b’Av.