I've made a huge mistake

Good: Quickest response to query letter EVER. (and my name was spelled correctly)

Bad: It was a rejection.

I'll bet Jason Bateman doesn't have these problems.

Worse: That probably means I didn't read some element of their criteria closely enough, i.e., submitting a teen romance novel to someone specializing in fly-fishing manuals. The clue? NO ONE evaluates a query in a half-hour... not even a query from a literary giant like myself.

The proper cliche to deploy here, I think, is "live and learn."