You are, because you are doing it.
I think a lot of us don't like to admit this little truth about ourselves. We all harbor this secret, and admitting to it reveals our weakness somehow. What am I talking about you ask?
Most of us will think of a con-artist or an identity thief after we hear that word. Which is exactly what we often feel about ourselves. We feel that especially in those moments when we are stepping out in to a new and risky venture. For me, it is this blog and my business. I fear that in writing and living my dream as a film producer, I will eventually be exposed as a fraud. Someone will "find me out," and I will lose the respect of my community. This is more common than we think. So common in fact that it has been given a name: Impostor Syndrome. Read more about it here: https://en.wikipedia.org/wiki/Impostor_syndrome
I would postulate that most people feel this in some shape or form in their life. Maybe they don't feel like they are a good manager or a singer. Maybe they don't feel they are a good parent or teacher. Maybe they just don't feel like they are an interesting person at all. This tends to defeat a person before they can even take a step in the right direction.
Let me pose this idea to you; you get to decide what you are. That's right! You get to decide by doing it. That's it! You are a teacher, because you get up every morning and look at the lesson plan and create a course of study for your students. You are a parent, because you have set out a plan to create the best human being you can imagine. You are a business owner because you plan ways to grow and expand your business. You are a singer, actor, lawyer, business owner, etc because you are doing it!
You may remember hearing as a kid that you are what you eat. I contend you are what you do. So keep doing it!