Marc Marion at 2014-03-27 12:41:26:
Curse you SOS!!! This is something I've struggled with but never new it had a name until now! I'm always excited by new ideas, and often times when I was writing short fiction before, I'd get a couple months in to a project and boom, a new idea would hit, and the current project got scrapped in favour of the brand new shiny one.
I think it's a very natural feeling with new ideas. A new idea really is something shiny and glimmering you only see off in the distance and it looks so brilliant you can't help but feel pulled to go towards it. And inevitably, the closer you get, the more details you can make out, and that sparkly diamond on the mountaintop slowly starts to morph into a used candy bar wrapper :p And then you notice something much shinier on the hilltop just past this one, and it all starts again.
For myself, I realized this was an issue, so in my screenwriting I originally tried to resist the new ideas I would have, but that only seemed to make me think about them even more. And as writers, we all know that every idea might be that diamond, and you don't want to let any go. What works for me is giving myself a few days to go down the rabbit hole, explore this wonderful new idea, poke holes in it, imagine the characters that belong in this world... but always to come back to my current project. By giving yourself some time to play around with the idea, you may realize it's not as good as you first thought. And if it's good, you've captured the idea and started laying a foundation for a future project that you can easily come back to later, and you have that peace of mind that you can let that new idea go, but that you've put in somewhere safe to come back to. And if you're really lucky, and you can be objective, that new idea might prove to have so much potential, commercial viability, and hits a chord deep within you that it is worth scrapping your current project and moving into this new idea.
So my whole-hhearted recommendation in order to get the best of both worlds, is to allow yourself some time for recess to explore new ideas when they come up, but set a timer and when the bell rings, it's back to work.