Whenever I have a great new idea, there's a tricky decision that has to be made.
Do I Google it to find out if someone else is already doing it, or do I just press onward? 
There's pros and cons to either choice, and there are times when either choice is the right one.
The former can kill your excitement, but the latter can waste your time.
The former could provide you with excellent research and insight that might make your idea better, but the latter could ensure your ideas are "untainted" by the ideas of others.
Here are the ways I handle these situations:
1. I quickly dump all the initial thoughts I have out on paper.
2. I savor the idea high. It's life-giving.
3. I ask myself: "How much does it matter if someone else is already doing something like this?"
4. If the answer is "not much", then I don't Google it until I've had time to fully flesh out my idea independently of knowing what others are doing. 
5. If the answer is "a lot", then I don't waste another minute on the idea until I've done a quick "saturation check" (i.e. is the "market" too saturated).
6. If the saturation check tells me the "market" is too saturated, I put that idea in my archive and move along.
7. If the saturation check tells me the "market" doesn't have much of my thing, then I go back to exploring my idea.
8. I only do a thorough Google search and research phase once I get my idea fleshed out. At this point, it's necessary to understand what other people are doing.