What writer doesn't need a little PATIENCE?
Honestly, it's one of the fundamental instruments in the writer's toolbox.
Let me put it into perspective. I wrote my first book in 2008. I spent six months waiting for my beta readers to finish reading it. I spent another year submitting it to agents. It took me a year because some of them took so long just to reject me and others took even longer to read the partial or full manuscript requests they asked for. By then, I gave up on that work and started another one. I finished Scar-Crossed at the end of December in 2009. My betas didn't finish reading it until May of 2010. I started submitting to agents and didn't sign with one until October 2010. I spent nearly nine more months editing Scar-Crossed with my agent. I went on submission in New York in mid August and I'm still there. I could be there for another year. When I do get signed by a New York publishing house it will take 1-2 YEARS for my book to be published. Every single day SOMEONE asks me, "Are you published yet?!"
All I can do is restrain myself from beating them over the head.
So yeah, be patient. Sometimes it takes a really long time to hear back from agents. It usually takes longer to hear back from editors.