God gave you the child you have. He knew exactly who he was making, even before the child was born. He knew each child's parents, before the parents were born. Your child has been placed in your family for a reason; formed in your womb, delivered into your family, with all their days ordained and written down, before we even knew them!
For you created my inmost being; you knit me together in my mother's womb. I praise you because I am fearfully and wonderfully made; your works are wonderful, I know that full well. My frame was not hidden from you when I was made in the secret place. When I was woven together in the depths of the earth, your eyes saw my unformed body. All the days ordained for me were written in your book before one of them came to be.
What a comfort to know that God has provided this whole arrangement. You will succeed at homeschooling high school, because your child has been given to you - because God knew in advance this day would come. He knew what you needed for this day, and he can provide.
I can do all things through Him who strengthens me.
When you look at homeschooling high school, DO NOT PANIC! You are completely capable of doing this! Your child has been given to you - it's been planned this way forever! You have what it takes to do the work - God promises to strengthen you! This is a completely doable task.
The secret of your success will be the love you have for your child. The love of your child will teach you what they need to know, how they learn, what they are missing, and how to prepare them for the future. Love won't teach you calculus, but you don't need to know calculus in order to homeschool high school. Instead, the love of your child will motivate you to find a way for it to happen. Love will urge you to seek resources and curriculum choices that will fit your child.
1 Peter 4:8
Above all, love each other deeply, because love covers over a multitude of sins.
The love you have will cover the difficulties you face. You will fail at some small tasks, because we all fail at small tasks every day. Even high-powered professional executives will fail at small tasks regularly. But we will succeed at the big task: raising and educating our child.
Your child has been given to you, so you know you can homeschool high school. You know you are capable, because you have the strength of the Lord behind you. And when small missteps occur, the love of your child will cover you.
You will be successful. Do not be afraid.
For more help overcoming fear, read my article "Homeschooling High School Without Fear."