How often do you ask yourself: why do I do what I do? Why my employer employs me? Why is my business successful? I don't do it very often; in fact, in everyday rush, I often forget what's important. I lose the "why" from horizon. It's a mistake - but it's a common one, made by individuals as well as large companies.
Simon Sinek in his TED talk described, why big, innovative leaders can change the world. Using examples like Wright brothers and Apple, iPad and aeroplane, he shows that the main source of success is the vision.
To achieve positive results of your projects, you and your team must be well motivated. Without proper motivational mechanisms, people could easily lose their productivity, get apathetic and bored with your project.