Why do Mormons go on missions?

I just recently finished a mission to Montevideo, Uruguay, South America. I decided to go because I know it was a commandment of God, and that He had given me so many blessings in this life that I couldn't possibly refuse this call. I saw the joy that came into many people's lives as they accepted Jesus Christ as their Savior, repented of their sins, and began to figuratively feast on all the scripture he has revealed since Biblical times. Many accepted baptism, which is an essential ordinance, or ceremony, to bring us closer to God and allow us to live with him again.

Of course, when you serve the Lord, you receive even more in return. My own testimony grew. My knowledge, my patience, and my ability to love, were all increased. I grew more close to my Heavenly Father in those two years than I could have ever done on my own. We go on missions because everyone is a child of God and needs to live His restored Gospel to live with Him again. Everyone needs an opportunity to accept or reject it. And we as people grow immeasurably by serving our Master and our King, even Jesus Christ.