Back in Mosiah 28:1–10, the sons of Mosiah gave up power, privilege, and comfortable surroundings in order to preach the gospel. Each of them declined to become the next Nephite king and, instead, risked their lives to teach among the Lamanites. Similarly, while serving as the Chief Judge among the Nephites, Alma saw that the Church was starting to slip seriously into pride and iniquity. In response, he "delivered up the judgment-seat to Nephihah" and "confined himself wholly… to the testimony of the word, according to the spirit of revelation and prophecy" (Alma 4:18, 20).
The accounts of missionary service in the Book of Mormon, largely contained in the book of Alma, provide important examples of faith and righteousness. Just like the missionaries in the Book of Mormon, today’s missionaries make real and burdensome sacrifices as they respond to the prophet’s call to serve. This may mean giving up an academic or sports scholarship, postponing educational or career opportunities, or leaving behind family members in times of financial or emotional strain. Whatever the sacrifice, the Lord will always bless those who faithfully serve. The act of submitting papers to serve a mission and then accepting the call to serve in a specific area of the mission field is a great act of faith on the part of every missionary. The young proselyting missionaries for The Church of Jesus Christ of Latter-day Saints do not choose where they serve. They go not knowing beforehand where they may be sent and what they may be asked to do—much like Alma and the sons of Mosiah.
Book of Mormon Central, "How Does the Book of Mormon Prepare Missionaries to Sacrifice, Serve, and Preach?" KnoWhy 333 (June 30, 2017).