I think you pretty much know my viewpoint on the "teenage years". They aren't magical or exceptional, other than in the sense that they are a continuation on growing and maturing that you've been doing all along. Each year is a milestone, with it's own highlights and challenges. Adding "teen" to your age doesn't change that.
And it doesn't have to turn you into someone you don't recognize. More than ever the world will demand that you turn your back on what you know is true. It will lie and tell you this is the time to "try new things", code for rebel against, mock and twist the truth. It will tell you that you need to "find yourself". Don't listen, you know the Truth. His name is Jesus. You are *so* faithful to Him, and focusing on Him will never be a bad choice. It will always lead to real, abundant, life. These things have been true all your life and they won't change now. We have always encouraged you to learn all you can about Him, to listen to His leading, to believe that the Holy Spirit teaches you and guides you. Don't follow your heart, or your dreams! Those selfish desires will only lead you astray. Follow Him, follow His vision for you. Follow His heart.
You have amazed me your whole life with your passion for Christ. As you become more and more autonomous, gaining new abilities and responsibilities you will be able to do a wider variety of things for the Kingdom. You are already gearing up for some big opportunities, deciding to do hard things, trusting that He will go before and behind you. Keep saying "yes!" to Him.
Your challenge is the same as it has always been: fighting the fear that everyone seems to think is necessary. That is the biggest lie you will hear. Fear is absolutely in contradiction to everything the Word teaches. Over and over we are told, "DO NOT BE AFRAID!" You do NOT have to fear-He is with you. I am learning this, too, but I am here to encourage you. I am here to remind you. I am here to stand beside you. I can't do if for you, but if I can, I'll go with you. If I can't, I will be waiting to hear your stories of victory through Christ, to cheer you on, and to bring the ice cream.
And never, ever forget how much your Dad and I love you. The hard things we make you do are to help you to continue to mature in who Christ wants you to be. Our chief desire for you is to grow in the love of the Lord and walk in His ways. Your education, your extracurricular activities, your free time, those are all tools to reach the goal: loving the Lord your God with all your heart, with all your soul and with all your strength. I have no expectations for you other than to follow His leading.
Make the most of Jesus. Leave the things of the world behind. I've said these things to you since you were born. These years ahead, they are just about continuing that journey. My fervent prayer for you is that in every way you will far surpass the faith that I have. I am always here to encourage you in that. I love you, my sweet, bright, lovable, Christ-like girl. That is never going to change.