I know I write about this a lot, but I came across this quote attributed to Johann Wolfgang van Goethe recently and no matter who actually wrote it, this gets the point across.
No matter what you want to do, start doing it. If you are terrible, then you are terrible, but practicing is what will make you good. If you are scared, good. The things we are most scared of are usually the things we should be doing. If you don't know if it is right, then try it. How will you ever know unless you try? What if you fail? Then you try again.
We spend so much time thinking about whether or not we should do something that we make starting the hardest part. Stop thinking so much and just get started. Starting doesn't mean the world is going to be figured out or that you have to keep doing it the rest of your life. Starting just means you have taken the first step...you have gotten past the hesitancy and you have begun. Starting is neither the end of the world or the change you have been waiting for.
Starting is the first step (of many) down the path you want to follow. Just like every other path you have followed in life, there will be many other branching paths you can take as you move along it. Starting doesn't decide everything; it just gets your ass in gear. Starting doesn't commit you to anything, it just allows you to move forward. Stop standing still hoping change will come to you. Whatever it is you want to do, begin today. No more hesitation, no more fear, no more over-thinking...just start.