Querying agents is like asking someone to the prom. You want the one asked to feel special, not like "I'm only asking you because none of the popular girls would go out with me." To stretch the metaphor, I give a big #agentfail to agents who complain about the number of queries they get. Oh really? 500+ guys have asked you to the prom this month? And you just can't decide which of them to go with? Gee, must be tough being so reputable and popular. Sure, I appreciate that agents have a hard job, but so do I. Quit whining. (Er, them, not you, Janet :D)This is a good analogy. But maybe not a great one.
It is meaningful for editors and agents to remember the compliment many authors are paying us when they query.
(This is sometimes hard to do, because some of the people querying us are not complimenting us. They clearly know nothing at all about us--whether that's proven by spam emails or through querying something we don't represent/publish. Those queries are the equivalent of the guys who shout propositions at you from moving cars.
Those queries aren't "I think you're pretty and interesting; will you go out with me?"
--they're "Hey you, with the tits!")
It's also meaningful for authors to remember that it's not 500 in a month. It's more like 1500. And like any highschooler, we have a lot of other things to do besides going to prom and dealing with hopeful dates. So it's tough on both sides.
It's fine to expect some sympathy from agents and editors. As long as it's ok for us to expect some sympathy from you.