With the new missionary age change...the number of missionaries who have been called has quadrupled and I would say SO HAVE the number of righteous young women(that's you) who are now writing or waiting for their missionary!
Now the first thing that someone is going to tell you is that it is not going to work. Try not to listen to these nay-sayers! You follow the Spirit for your life. They do not know the Lord's plan for your life.
I want to give you encouragement that it CAN work, if it is right. Also be open to the fact that you may grow apart if it is not right. The most important principle: Follow the Spirit!
Many years ago, I "waited" for a missionary. I knew it was right 100%, it was just a matter of writing and waiting! Then when he had a year left, (I made it half-way at least) I felt VERY strongly that I was supposed to serve a mission of my own.
This was a VERY hard decision to make. It took all the faith I had inside of me at the age of 20 to leave my plans, (notice I said MY PLANS) and follow the Lord's plan for my life...and that was to serve a mission.
My missionary actually ended up waiting for me for almost a full year before I returned home. It was right, and the Lord blessed us immensely.
We were married a few months later and serving a mission was the right decision for me. I was a much better and stronger version of myself and I was now ready for the next chapter of my life.
So I am here to tell you, it CAN happen, and it CAN be right, IF it is the Lord's will. But you have to be open to listen and follow the Spirit!
How to Wait
You still have to live and be a normal young adult. Date, hang out with friends, have a job, go to school, be involved in bettering yourself. Prepare yourself for your future!
There will never be a time in the missionary's life when they are closer to the Lord than they are now. They are growing and learning by leaps and bounds each day. A general authority once said, "it would take an average church member 40 years, reading and studying 30 minutes a day to equal that of a missionary"
You cannot compare anything to missionary work. Nothing compares.
So you have a lot of work ahead of you to stay strong and spiritually ready for him.
What kind of letters to write?
Write him supportive, not mushy letters.
This is a great time for you to grow and build your testimony right along with him. Send him favorite scripture passages you have read that have touched you. Favorite quotes. Share your testimony! Tell him how proud you are of him and that you know he made the right decision. Tell him you are praying for him. Encourage him to be completely obedient.
Be careful of what you write or send in the email. Remember- he is not yours right now, he is a servant of the Lords. Support him in what he has been called to do!
Can you end the letter with an I love you? Pray about it and feel it out. I think it is OK to end a letter with that encouragement, just make sure that is not what the whole letter is based on.
Lastly, just be yourself. Write like you talk. Don't worry about how to say things or if you are saying things wrong. Be yourself, but be supportive. Try not to distract from the Spirit.
Will it EVER get easier?
Yes and no. The hardest part will be the first month. You will probably feel every single day pass. You will miss him and feel like someone just ripped out your heart. It will be heartache like you have never felt before. The thought of 2 years will completely overwhelm you!
BUT it will get easier! I promise!! You will get used to it and will become stronger through this. Lean on the power of the Atonement of Jesus Christ! Lean on the power of scripture study for comfort and strength. Lean on the power of prayer and learn to really pray. Lean on family and friends to get you through.
If the timing is right, the new missionary age change allows you to go out at the same time as your missionary! How cool would that be to serve at the same time?!!
Just know, one of the hardest things a young woman can do is to say good bye to a best friend as he goes out to serve a mission. But it will be totally worth it! It will be an experience you will never wish to be taken away from you.