Just as surely as each person living on this earth entered by the birth process, each person will die at the end of their sojourn here. 1 Corinthians 15:20-22 Together the spirit and body make up the soul of humans, whether they want to admit it or not. Earthly parents are co-creators of mortal bodies, but the spirit is much, much older than the body. God, The Father, created spirits who all lived together in Heaven, waiting for their turn on Earth. Hebrews 12:9
Once on Earth, all are given to know right from wrong, good and bad, false and true, even if they aren't blessed to learn Jesus' gospel. All are expected to choose the right way according to the light and knowledge they are blessed to obtain. All will be judged according to their works on Earth. Revelation 20:12-13 Of course those that choose to follow the Savior will be happier on Earth, because they can repent and allow His Grace to bring joy to their lives. 2 Nephi 9:10-11 Alma 5:15-21
All will die, because Adam brought death into the world through the fall. Nevertheless, the fall also allowed men and women to experience opposition. It is only through opposition that mortals can learn to recognize true joy. 2 Nephi 2:22-25 However, opposition also gives humans the negative opportunity to choose improperly and need to repent. Alma 34:32-33 Good works, grace, and repentance will allow us to have a fullness of joy, peace, and rest in the hereafter. Alma 40:11 This life was never meant to be heaven; that comes later. It is for testing and choosing and discovering the right way to be happy. Alma 42:5-15 That's not to say mortals can't experience joy and glimpses of heaven as they continually grow closer to God, the Father, and His Son, Jesus Christ.