I'm so excited that Captain Awkward, whose work I adore and have studied closely while developing my own advice column, has kindly linked to Story Hospital.
Books often change quite a lot as you're writing them and the book you've written may require a somewhat different protagonist than was called for in your original outline.
Inspiration is intermittent and fleeting, and writing without it feels unsatisfying or clumsy by comparison. So we chase after it and try to get inspired again, or we give up on the old project and start a new project, as though that were the only way to write well, or to enjoy writing. It's not.
If no one reads your stories about queer girls in space, that's not a judgment on you. And if everyone loves your stories about queer girls in space, that's not a judgment on you. The work is the work.
Over time, as you write more, you will learn to recognize which ideas can be developed easily, which can be developed painstakingly, and which can't be developed. And you will learn more about your own process of development, which will help make both easy and difficult development go more smoothly.