I have to say people, finish what you start. There's always a shinier idea somewhere ready to come along and grab you by the shoulder. That's the nature of our imaginations, and it's a normal part of writing avoidance.
Look at me, now, with a 600,000 word project on my desk of which I've written 200,000 words only to be interrupted by chemotherapy. How could I possibly manage such a project if every neat idea I had in the mean time interrupted me?
Furthermore, if you don't finish what you start, you've got nothing to sell. Six or eight or ten unfinished novels are worth less than one finished novel. Heck, an infinite number of unfinished novels are worth less than one finished novel. If you don't have the discipline to follow through an idea when the middle gets muddled and draggy and boring (and they all do that when you're in the middle of writing a novel), you don't have the discipline to be an author.
I've written through parenting crisis, emotional disasters, mental stress and distress including anxiety and depression, busy times at work, illness, you name it. In the eleven years since I became a pro, chemotherapy and surgery are the only things that have been able to stop me cold, and believe me, if I could find a way around that, I would. There are no excuses except the ones you make up for yourself. Even with chemotherapy and surgery these past two years, I've managed about 250,000 words of first draft each year.
If you want to be an author, finish the project. Then write the next project. Being a pro is that simple, and it's that hard.
What is it that stops you from writing?