"A now, my son (my grandson Cameron), I trust that I (your grandmother who loves you dearly) shall have great joy in you, because of your steadiness and your faithfulness unto God (remember how excited you were to attend the Temple for the first time and how much knowledge you have of the scriptures); for as you have commenced in your youth to look to the Lord your God (I remember you relating the Book of Mormon stories at Lake Powell during our Sunday School lesson. How proud I was that you have listened as your mother and father have read the scriptures to you). Let them sink deep into your heart, they are not words, but a testimony to you of who you are and how much God loves you.), even so I hope that you will continue in keeping his commandments; for blessed is he that endureth to the end." (From this point in your life, you are going to have lots of temptations, don't yield to them, keep the commandments, continue as you have started.)
Answers to your Questions:
Here are the questions you asked about missions. I appreciate your insights. Let me try to give some answers.
-- Why are we commanded to go on missions?
Because you are a solider in God's army and he needs all the righteous men and women he has to teach others about him, the atonement, the plan of salvation, and what life will be after we leave this earth life.
-- Is it worth it to go?
Worth it, you bet it's worth it. There is one purpose in our life and that is to return to our Father in Heaven and enjoy everlasting life with him. So many people around the world do not know that as their purpose. We need you and so many others like you to stand up and give this message to them. That alone makes it worth it to go, but even more than that, the changes it will make in you make it ever so much more worth it. You will learn so much. You will find out what true service is. You will learn to sacrifice and you will learn about you. Yes, it's worth it.
-- Are the experiences you have there fun or just spiritual?
All your experiences will be fun. Imagine how fun it will be to walk into a baptism font with a person you have taught and baptize them? You will have a great time living with other 18-20 year old young men and learning about how they were raised and how they grew up. You will grow to love them more than you can imagine, they will become great friends to you. Yes, you will get to play volleyball, basketball, soccer, (probably not ice hockey), sing, learn new talents, maybe a new language and give service to people you don't even know.
-- What are some of the lessons you teach?
You will teach about the first vision of Joseph Smith which is the restoration of the gospel for these last days. You will teach them what he learned about God, that he is a real person with flesh and bones just like us and he son Jesus Christ. You will teach people to pray, to read the scriptures, to gain testimony through doing the thing that we are commanded.. You will teach all about the Book of Mormon. Think today - what are your favorite stories, scriptures and messages? If they are of interest to you, ask yourself why? Then think about why they are important to you. As you attend Seminary next year, you will learn the Scripture Mastery scriptures and many lessons. That's your mission training ground. Listen and learn. Memorize as many as you can, it will help you on your mission.
-- Why should we go on a mission?
Our Father in Heaven has given us everything. A mission is your way of giving back to the Lord a tithe of time, commitment, energy and love. You will be 18 or 19 when you decide to go. Think of a mission as that tenth of your life; the prime of your life that you will give to the Lord.