For those that are not sure what is being described here or have answered hastily, this is a subject worth looking into. Read the book by Simon Sinek - Start With Why. There is also a short YouTube video he did on the subject. But starting with your 'Why' should not be something you can answer quickly if you REALLY get to the true why.
Why has to speak to the soul of who you truly are. "I want to be wealthy" is not a why, that is the result of something. "I want to make money in real estate" is not a 'why' - that is a what or a how.
It took me over a month to come up with my why, and I ended up coming up with something that in the end became more of my life's 'mission statement' if you will:
My Why - To focus the efforts of my life toward things specific to the service of those I care for, the acquiring of wisdom and knowledge for myself, or to gain understanding into the mysteries of the nuances of life.
That is me to a T. Now WHAT I do has to fit into my why. That in the end is what makes people truly happy. I realized that my corporate america job does not fit my why. And even though I enjoy it I have to start to focus on something that gets me more towards my why, even if it takes years.
Again, I highly recommend reading the book.
"This book is not designed to tell you what to do or how to do it. Its goal is not to give you a course of action. Its goal is to offer your the cause of action." -Simon Sinek