In the book of Alma, Amulek says that “this life is the time for men to prepare to meet God”. I always thought that we lived with God in the pre-mortal life. If so, haven’t we met him already? Why did he send us away just so we could prepare to meet him again?
In the Book of Moses, Ryan, the Lord declared, “For behold, this is my work and glory — to bring to pass the immortality and eternal life of man” (Moses 1: 39). In order to comprehend the answer to your question, why we prepare now to meet God, is discovered by understanding the “three pillars of eternity” as provided by Bruce R. McConkie,
“There three pillars of eternity, the three events, preeminent and transcendent above all others, are the creation, the fall, and the atonement. These three are the foundations upon which all things rest.”
What is the purpose of our creation and the earth’s creation — the first pillar? As you have already stated, we know that we lived with our Father in Heaven before we received our tabernacle of flesh and blood. Our Father in Heaven already was tabernacled with a glorified immortal body of “flesh and bone.” In our pre-mortal life we were taught the principles of Deity by precept and example as we lived with our Father in Heaven. As we lived with our Father in Heaven, a plan was presented by which Heavenly Father would bring to pass our immortality and eternal life. This plan involved two spirits, Adam and Eve, to live in a garden, partake of forbidden fruit, and thus being cast out of the garden of Eden — the Fall — the second pillar.
In the book of Alma, two verses before your question, we read, “according to the word of God; and thus we see, that by his (Adam’s) fall, all mankind became a lost and fallen people” (Alma 12: 22). In other words, physical and spiritual death were introduced into the world by means of the fall. Physical death simply means that death was brought into our world, and by the means of death, our spirits and our bodies would become separated to rise no more, forever cast out of God’s presence. Our separation from God is our spiritual death. As such, this time became a time to prepare to meet God, how? Due to the third pillar of eternity — the Atonement.
As Bruce C. Hafen declared, “Yet because of the Atonement, they could learn from their experience without being condemned by it. Christ’s sacrifice didn’t erase their choices and return them to an Eden of innocence. That would be a story with no plot and no character growth. His plan is developmental–line upon line, step by step, grace for grace.”
This life provides opportunity for us to progress, developmental, toward two natures: Godlike or the natural man. Our bodies experience appetites and passions from opposites — good and evil. The more we use our agency to put off the natural man and become a Saint by yielding to the enticings of the spirit we prepare ourselves to meet God, because when we see Him we will be like Him; however, other brothers and sisters will not be prepared (they will be unprepared) because they used their agency to accept the will of the flesh.
In the Book of Mormon, during the wars with the Lamanites, we read, “Now, they were sorry to take up arms against the Lamanites, because they did not delight in the shedding of blood; yea, and this was not all–they were sorry to be the means of sending so many of their brethren out of this world into an eternal world, unprepared to meet their God.”
In light of these paragraphs, we recognize two types of people, those who will be prepared for the final judgment, and those who will not. Those who will be prepared are those who steadfastly perfected themselves in Christ, while those who are unprepared (due to wasting away their days of probation) will not be prepared for the final judgment. This time is our time to prepare for exaltation. If we waste away our time, then we will be unprepared to meet God.