You are depressed because you have fetishized the defense. It's almost impossible not to do, but nonetheless should be minimized as much as you can.
The defense is not: a defining moment of who you are as a person, a measure of your worth as a scholar, the pinnacle of your graduate experience, a moment of transcendent transformation from student to full professional peer, or the sign of your ability to go out and do whatever you damn well please without ever having to look over your shoulder again.
The defense is a technical hurdle to be overcome. It's a rare opportunity to get several experts together to focus on you and your work. It's a chance to get advice on how to move a project forward from draft to publication. And it is an important step toward emerging as an independent scholar, though not the final one.
Wallow in disappointment for a bit longer, and then see if you can shake it off and get moving again. Hang in there -- you will make it, and in five years, those two months won't mean anything. On the contrary, if they enable you to come closer to exiting your program with something that you can publish, they will have been a real boon.
It's academic hazing at it's finest.
"I survived, let's see if you can."
Actually, I was depressed after submitting the final version/edit of my dissertation to the thesis office....I was looking/searching/begging for something to do...I have been glued to the computer for so long, with so many deadlines, so much intense stress, that to have "nothing to do" was really unacceptable.
I've gotten over it. Really.