You Did Not Create a Flying Purple Elephant
Some people think they are not creative. I think many of them simply don't realize that it is impossible to create. Once you know that, it becomes a lot easier to be creative.
Let's say you are making a children's picture book about a flying purple elephant. You did not create elephants - they already exist. You also did not create the color puple - that also already exists. Did you create the concept of flight? Nope.
So what did you create? The combination.
Basically, that's what we creative people do, we combine things in different ways. Combine an evangeilical Christian with a serial killer and you get the movie Seven. Combine a ship's first mate with a dog and you get Chewbacca. Combine the reality TV show Survivor with a young-adult dystopian setting and you get The Hunger Games.
I could keep going for a while here, but I think you get the point.