I’m curious, how do you tell if it’s okay to resubmit when suggestions for improvement are made? Is it spelled out, as in “please feel free to resubmit”?
Anytime you make improvements feel free to resubmit.
Listen, I’m of the give it a try, put it out there, life is too short mentality. Life is too short to over think everything we do and how everyone will react to what we do. You will NEVER burn bridges by professionally, simply, and politely querying an agent. You will burn bridges when you react to a rejection by calling her an ass, an idiot, a fool, or a waste of your time, but that’s a blog for another day.
If you have a dream agent and you’ve revised the book so heavily that it really is a different book and the book you should have submitted in the first place it can never hurt to send a query. Truly what’s the worst that can happen? She’ll say no. Keep in mind if that happens, that “no” might not have anything to do with the fact that you are requerying. It could simply be that her list has filled with that type of book, her interests have changed, or she really just isn’t interested in taking a second look.
All of that being said, don’t spend a lifetime on one book. As best as you can, once the book is out on submission, become so engrossed in your next project that any revisions or changes you want to make go into something fresh rather than a constant rewrite of the first thing.