I get that all the time, what usually helps is;
A. Dress in black and put on eyeliner, then write crap gothic poems
B. Drink until you go blind
C. Listen to how bad someone elses life is
Results exprected;
A. Finish, then look at yourself in a mirror and re-read your poem and fall down in fits of uncontrollable laughter
B.Wake up after having done something interesting/stupid/illegal which will completely take your mind of your current problems
C. Makes you feel that perhaps God hates you just a bit less than someone else
If you're religious I find that this quote helps keeps you going;
Stan: WWhy would God let Kenny die, Chef? Why? Kenny's my Friend. Why can't God take someone else's friend?
Chef: Stan, sometime God take those closest to us, because it makes him feel better about Himself. He's a very vengeful God, Stan. He's all pissed off about something we did thousands of years ago. He just can't get over it. So he doesn't care who he takes: children, puppies, it don't matter to him, so long as it makes us sad. Do you understand?
Stan: Then why does God give us anything to start with?
Chef: Well, look at it this way: if you want to make a baby cry, first you give it a lollipop. Then, you take it away. If you never give it a lollipop to begin with, then you would have nothing to cry about. That's like God, who gives us life and love and health just so that he can tear it all away and make us cry, so he can drink the sweet milk of our tears...You see, it's our tears, Stan, that give God his great power.
Stan: I think I understand. ~ South Park
Just keep going on through it, it will pass!