One thing you need to know about writing: You'll never be quite sure about it.
You'll feel amazing one moment. The next, you'll doubt every word.
You'll spend the rest of your life trying to master the craft, except you never will. There's always something else to learn.
Sometimes, you won't even be sure about why you write at all.
But you'll write anyway, because it's the one passion in your life that's almost as important to functioning as breathing.
So don't worry about being unsure. That aspect to being a writer never goes away.
Get used to it.
What are you always unsure of as a writer?