If you're trying to get published, it's inevitable -- you will be forced to master The Art of Waiting, like it or not.
By now, I have just about mastered this "art." And I've got the war wounds to prove it. Just two examples: an article I got published in 2007 took 3 YEARS to see the light of day. I submitted a query, waited a few months. Got a request to see the full, waited a few more months. Got a "We're interested in maybe, perhaps, possibly publishing it, but would you be willing to make a few changes?" email, waited a few more months. By the time I went to the bookstore and got the edition in my hot little hands, so much time had passed that a tiny part of me wasn't even joyful about it. The grueling process itself had practically sucked some of the joy away.
Another example: a huge (I'm talking big-wig, best-of-the-best, stellar) NY agency requested a full manuscript of my novel. Then, they sat on it. For 18 months. I sent four VERY polite, professional email inquiries, but to no avail. Totally ignored. Finally, I sent a (still-professional) hard copy letter to the office, saying another agency was interested in seeing the full (which was true). The next day, I received a form email rejection, saying my material "wasn't for them." It took 18 months for them to decide that.
Those are extreme cases, and most of the time, agents/editors are very courteous to stick to their word, to their projected turnaround times.
But the main point is, if you're a writer trying to get published, you WILL be made to wait. It's a natural part of the process. So, what to do during that time? Try to forget about it, let it go, and KEEP WRITING.
As a matter of fact, right now, I'm awaiting a response from the agent who (very kindly!) requested re-writes on my novel. The holidays are a very busy time for everyone, agents included, so I really don't expect to hear anything before Christmas. This agent is a rare breed, in that she's been nice enough to keep me updated/informed about her turnaround time along the way, which has lessened my wait-anxiety.
Here's what I'm doing in the meantime - I'm pushing the agent situation to the back of my mind, and biding my time by editing the second book in my series. It's keeping me very busy - and very focused on something else besides the gnawing anxiety that I might get rejected. Or, heaven forbid, that I might actually get accepted!
So, remember - keeping busy and staying productive kills the frustration/anxiety/impatience bug. Well, maybe it doesn't totally kill it. Maybe it just maims it a little bit. ;-)