Often there's no way to know whether you're heading for a fall or for a bonanza.
The thing is, that doubt usually comes when you've already invested a lot of time and effort in the project and you might as well keep going and see how it all comes out.
That's hard to do when you've had a lot of rejection. I've had this experience with a novel I wrote a few years ago. It was rejected by several publishers for being too controversial and I decided to put it aside for a while. That while has stretched out to much longer than I planned, probably because my inner critic (whom I fired but who sometimes shows up for work anyway) whispers in my ear that sending it out again would just result in more rejection.
These inner critics do their work so sneakily that we don't even notice it. Now that I've noticed it I'm going to put that manuscript out into the marketplace again and hope that it'll be Florence Scovel Shinn, and not my inner critic, whose quote applies.