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Looking for a book featuring an Agoraphobic

Hey, sorry if this is the wrong place to ask this but I have been hunting a novel that I read many years ago but I cannot remember the name. Here is what I remember: It was written by a female author. The main character I believe was a "chosen one" kind of character where he had to go on a journey to a specific planet to fulfill a prophesy. The character that stuck with me was the main character's best friend who grew up on a space station. He learned at a very early age the safety of a confined, sealed space, and If you saw a large open expance, that there was probably a hull breach, and you were going to die, or have a very bad day. Thus when they arrived on a planet, he was extremely agoraphobic, and had a hard time functioning under an open sky. I just thought it was a really cool concept not too often explored in space based science fiction (that I've read anyways). Does anyone know what this book is? Thank you!