Over at Diana's blog, she's talking about querying agents with a new work when you've submitted another to them in the past. As with her, it never occurred to me not to submit my new work to the agents that rejected the last, whether it was a form rejection or a reject of requested material.
First of all, are they really going to even recognize my name? I mean, some of these people get (and reject) upwards of a hundred queries a day. Unless I have a really memorable name--and I ain't Saddam Hussein or Lizzie Borden--they're not going to remember lil' ol' me.
Second, as Diana says, my voice is still developing. In MS #2, I can almost see it, and in the current WIP, it's really starting to flourish. In MS #1? Bah. I was still getting a grasp on the basics there, so my voice is hidden deep under all the rookie mistakes, if it's there at all.
And lastly, and perhaps most mind-bogglingly, as I said over at Diana's, there's not an unlimited pool of agents out there. If you query twenty for your first novel before shelving it, then query thirty for your second...well, that's fifty agents added to your "they don't like me" list. Assuming that you're continuing your work in the same genre as the first two novels, it's going to be a huge PITA to find another thirty to harass with #3. Personally, I prefer to break out the same list I used before, make sure all the old names are still at those agencies and in the biz, add some new names to it, and go to town. In fact, that's what I'm planning to do in the next month or so (with MS #2).
I said it over there, and I'll say it over here. I'm going to keep trying until I run out of words to write...not until I run out of agents to reject me.
If you don't feel that you are possibly on the edge of humiliating yourself, of losing control of the whole thing, then possibly what you are doing isn't very vital. If you don't feel like you are writing somewhat over your head, why do it? If you don't have some doubt of your authority to tell this story, then you are not trying to tell enough. --John Irving