Writing isn’t like masturbation. There’s no instant gratification. The problem is that you can have a difficult time finding the off switch to your creativity, an inability to tell your brain to stop coming up with new ideas until you’ve finished the book you’ve already started. And the sick irony is that you need your brain to think creatively in order to write in the first place.
What you need is an idea notebook, a convenient repository to jot down your ideas as they come to you. Sounds like a no-brainer, but it does wonders. I keep a journal as a hobby, and I often write down my notes and thoughts on the writing process in it, but that’s not enough. Matters of everyday life get written down as well; there’s at least a complaint a day about how little sleep I’m getting.
With that in mind, I recently bought a small, plain blue notebook. Dedicate each page to one story idea. Write the rough idea, key sources of inspiration if you have them, and maybe a couple of possible titles to toss around. Now, if you’re working on a story and it doesn’t work out the way you’d hoped, you don’t have to freak out about where your next idea is going to come from. Just tick a mark on that abandoned project, turn the page, and move on to the next one.