I've heard people say agents are just failed writers a couple of times. I read those sentiments again today in a blog post, only it was about editors and critics.
Consider this: the one person who knows how really hard it is to write a good novel is the one who has tried to do it.
I've failed at a number of things. I won't enumerate them but let's just say I know there are a number of things I'm not very good at. Every time I see someone do one of those things, and do it well, I know it's not just luck. When I see someone do one of those things and make it look effortless, I know I'm seeing thousands of hours of practice and a singular devotion to excellence.
I know this from actual experience so my understanding isn't just cerebral, it's visceral.
The next time you're tempted to believe agents and editors don't understand you, you might want to think that maybe they understand all too well.