Here's something all writers have to learn...usually the hard way:
Your writing is not perfect the first, fifth, or one-hundredth time. Believing that what you write can be perfect the first time is delusional. Walk into a book store, pick up any book (including classics that have been published hundreds of times) and find one without an error. You can't. It doesn't exist.
Writers, editors, and publishers work very hard to find those errors and remove them, but something is always missed. An army of people reading, proofing, and editing will still miss a couple of mistakes. As authors, we're even more likely to miss our own mistakes than anyone else. Have you ever heard the phrase, "You can't see the forest for all the trees"? It's an accurate analogy. Writers are so close to their works that you miss the mistakes because your brain knows what you MEANT to say. You know that "teh" was supposed to say "the" and therefore your brain actually sees "the." A good editor or proof-reader will catch little mistakes like this, but what about when you accidentally change a character's eye color? Hair color? Dominant hand? Eventually, you might find those mistakes, but more likely it will be a canny reader who spots the error and you end up feeling foolish for missing it. Some errors are even deeper than that -- with repercussions that only occur in later books.
I'm not saying this to make you, or even me feel bad -- I kick myself enough, I don't need the extra booting. I am saying this to hopefully help anyone reading this understand that perfection fresh out of the gate is not a reasonable dream. It is a fantasy that we all hope for, but it isn't logical. We are human (most of us, right?) and therefore we err.
Another aspect of being less-than-perfect is to remember that writing is a journey. The first book might be good, but the second will be better as will the third, fourth, fifth, etc. Everything we write is about learning who you are as a writer and creating a voice that is all you and that grows with you. Don't be afraid of the recommendation to "find your voice" in writing. All that really means is that, with practice, you will improve and become confident. You will still make mistakes, but they will be fewer and less obvious as you progress. Writing might be a genetic gift (though I doubt it) but it is like anything else -- you must practice, hone, and push yourself in order to get better. Don't be afraid of the mistakes. Be afraid if you cannot find any or don't learn how to fix them.