One of the great writer’s myths is the one about papering the walls with rejection slips. There are stories of proposals and manuscripts that were rejected twenty-five or thirty times and went on to become published books and even, in rare case, bestsellers. But these stories are so exceptional that when they do happen they immediately become part of publishing lore.
Part of playing the publisher’s game is knowing when you have lost. If you have been flatly rejected by ten well-chosen editors then you will almost certainly be turned down by the next hundred. It would be far better to spend your time rethinking your idea, reworking your proposal, or maybe even abandoning that particular idea and moving on to something else.