The teaching, then, is that if it weren't for Adam and Eve taking the fruit of the tree of knowledge of good and evil, they would not have had children (2 Nephi 2:22-23; Moses 5:11), so none of us would have existed. In the Garden as only a couple, neither would they have known good and evil, so they would not have known redemption and eternal life with the Father (Moses 5:11).
Adam and Eve's transgression made our existence and redemption possible. It was part of God's plan for them and for us that they would not remain in the Garden, but would be put into the world, outside his presence (Moses 5:4)
I find it interesting that though the Doctrine and Covenants specifies that through the fall Adam and Eve became subject to the will of the devil, a Book of Mormon passage says that they (and, by implication, we) "became subjects to follow after their own will" (Alma 42:7; italics added). Without God's grace, our will and that of the devil are the same in some profound sense.
But the Lord has made it possible for us to receive his grace, to repent of following our own will rather than his, to be baptized, and to receive the gift of the Holy Ghost. As Paul teaches in Romans (Romans 8:1-9), the solution to the problem of the weak will is to have our will be the will of the Spirit—of God—rather than that of the devil. We believe that change is made possible by the gift of the Holy Ghost, the privilege of having the Holy Spirit as our "constant companion" (D&C 121:46).
But also because of the fall, we find it possible for us to return to God's presence, not only eventually, after the final judgment, but here and now, in this life. Mormons teach that those who, as a result of their faith in Jesus Christ, repent and are baptized and then receive the gift of the Holy Ghost are allowed to enter into the divine Presence again.The way into God's presence is opened for them (Jacob 6:11).
Through repentance and its fruits, the rift between human beings and God is healed in anticipation of the eventual healing to be had in God's eternal kingdom. In an important sense, the fall can be overcome in this life.