Writers have an addiction to shiny things. Specifically, the Shiny New Idea. If you're anything like me, the Shiny New Idea process goes a little bit like this:
Some of us get Shiny New Ideas a lot. We're just walking down the street, minding our own business, then--BAM! As Gru put it, "Light bulb!"
But, more often than not, this Shiny New Idea appears to us while we have another work in progress going. And all we want to do is stop and work on this SNI. It's so much cooler and better than your current WIP. We should drop everything to work on it, right?
This is the literary equivalent of cheating on your spouse for a one-night stand. You've worked so hard on your WIP. Why should you stop now, just because something that looks shiny right now came along? It's not fair to your current characters.
You can't just stop working on your WIP every time a SNI comes along. You'll never finish anything, which will lead to you feeling discouraged, which isn't good. All you'll end up with is a large pile of unfinished manuscripts that'll never go anywhere and never see the light of day again.
If a SNI happens to come along, great. Having lots of ideas is never a bad thing. Start a special notebook or computer file to write them down. Hide them under a bushel basket (Yes, a bushel basket. Yep.) and don't let them come out. Leave them alone.
Did you catch that? Leave them alone.
But, Annie, if I don't start writing this amazing SNI right now, I'll forget all the wonderfulness and I'll have missed my million-dollar publishing contract opportunity and bla bla bla.
No. Don't do it. Fight the irresistible urge, my friends. Resist the urge to write it. So what if you forget it? If you can't remember it, it was never a good idea to start with. If you're afraid you'll forget it, then it's not worth the trouble of even thinking about.
Go back to your WIP. Finish it. Revise it. Make it wonderful. Then start going through your notebook of all the SNIs you've accumulated while working on it. You'll notice that some of those ideas that seemed so awesome at the time are actually quite boring and unworkable. And then you'll be glad you didn't stop to work on them. You'll have saved yourself many long hours of typing away at a manuscript that'll end up in the trash anyway.
And that other idea, the one that you thought of five months ago and wrote down in that notebook, the one that still looks amazing, the one you can't stop thinking about? This is the book you will write. This is the SNI that stuck with you. This is an idea with promise, because it still looks shiny, even now. Write it.
To make a long blog post short, don't start a whole new book just because of a Shiny New Idea you had last night. Never, ever, ever. Save it for later, because, chances are, it wasn't really a good idea to start with.