When you think big, you're exercising your brain-power to its full potential to come up with solutions, even when you fail, you've succeeded in knowing one way not to go about it and most importantly, you're building your boldness, for at times it is not that you are bereft of ideas or beautiful thought processes, the problem with some people (if not most people) is that they lack the boldness and confidence to take the bull by the horn and achieve the greatness they so desire. Despite all the opportunities that have come acrossed some folks ways, they'll still prefer to stick to the comfort and security of their day jobs.
Thus, in my own opinion (which kind of works for me-99.9%), I always dream and aim very high, even when everything around me tells me it is impossible, for we all know, we all have only one life to live and chances are that we might not have another opportunity to take up those wonderful chances we kept on dismissing from our mind for fear of failure.
So, we can all aim for the stars, if we fail, we'll land on the moon, if we fail to land on the moon, we'll land on Mount Everest, if we fail to land on Mount Everest, we'll land on a Skyscaper and if we miss the Skyscraper, we'll end up landing on the Roof-top of our House. Then, we'll get down and start all over again until we land on the stars.
Keep Striving, Keep Believing, Never Give-Up. Winners Don't Quit and Quitters Don't Win.