Why do Mormons go on missions?

Mormons go on missions because we have been blessed by the lord so much we want to help other people have this same kind of joy. I just returned from a mission in Arizona Phoenix; out of all the people I taught on my mission I believe the person that changed the most was me. Yes I helped people come to Christ by receiving the restored gospels, yes I helped them increase their faith, yes they repented were baptized and received the gift of the Holy Ghost and I hope they are enduring to the end. But I see myself now as a different and entirely better person than I was when I left. Why do Mormons go on missions to help others come unto Christ which also includes ourselves.