I personally think this is a good problem to have. If we didn't have ideas, we wouldn't be able to write a story. A lot of times i'll be working on one manuscript when inspiration hits. It can be a tad distracting, especially since I'm trying to focus on one thing and not on a hundred, but that's just how my brain works. Instead of putting it aside, I write down the specific scene that attacked my imagination so I'll remember it for later. I used to work on multiple projects at once, but that didn't go so well since I never finished any of those manuscripts. So now I write down little bits here and there when i feel inspired, but use most of my attention on just one thing. It took time, guys. I'm easily distracted.
As writers our greatest asset is our imagination. It's what we use to create new worlds, to find those beautiful perfect words to describe it, it's how we thrive. I love making stuff up in my head, it's great to have voices talking to me (not sure I should say that out in public, but you get my point), those voices drive us with their need to be spoken and heard. So don't ignore them. A lot of times I'll read tweets from other authors cursing the shiny new idea, but guess what, that shiny new idea ain't gonna go away unless you do something about it. If you're not feeling inspired by what you're currently working on, I don't think you would be cheating by starting that pretty idea, in fact I would encourage you to do so. Your lack of enthusiasm will show up in your work. For me, once I get that idea written down and squared away for later, the enthusiasm I need for my current project returns.
What about you guys, do you guys give into that distracting and eye glaring new project? Or do you push it aside for another time?