As a writer, one of the realities that you have to face is this: Rejection is a big part of the game. Not everything you send to an editor is going to be accepted and bought. More often than not, it'll be rejected.
You need to face that, take it graciously -- not take it personally, and move on.
Here's an example of someone NOT facing disappointment graciously.
If you find yourself reacting like this to rejection, perhaps you shouldn't be in the writing game. Not unless you're interested in having a stroke.
And one last note, no matter how frustrated or disappointed I have ever been when something didn't go my way, I'm proud to say that unlike the guy in this video, not once have I ever been so upset that I tried to shove a remote control up my ass. (There's some sort of ode to George Carlin in that sentiment, isn't there?)