A vision, an idea, and the ability to see beyond. We always push the limits, and we always figure out just how to transform our imagination into reality. To say that everything has been thought of is like stopping all innovation after the creation of the first wheel. Everything that you see around you was created or built by someone at some point. Everything is derived from something, and usually that something is nature. There is always room for improvement, and there is always something new to design. Also, just because you choose to improve on an existing design or create a similar product that is already in existence, it does not mean that is has been done by you. Your talents and skills and unique and so is your thought process. If you do not go for it, they world just might be missing out on something great. Every product, every company, and every design used to not exist at some point. It is up to you to introduce your rendition of it the world.
To all the engineers, designers, creators, and entrepreneurs: there is no limit to what you can accomplish, and there is no limit to what you can do. Just because someone else does not understand it, it does not mean that they are ahead of you telling you to turn back. They are more than likely behind you pulling you backwards. Never give up, because what you think is nothing today, can be something great tomorrow.