Before we can really determine what the fruit of good and evil was, we must examine the tree that produced it, the Tree of the Knowledge of Good and Evil. In order to do that, we must first grasp the true meaning of the Tree of Life, which stood next to the Tree of the Knowledge of Good and Evil in the Garden of Eden.
In Prov. 13:12 it says, "Hope deferred makes the heart sick; but a desire fulfilled is a tree of life." This indicates that for fallen man to accomplish God's will, man is to become a Tree of Life. Also, Rev. 22:14 says, "Blessed are those who wash their robes, that they may have the right to the tree of life." This verse indicates that the attainment of the Tree of Life is the source of happiness for fallen man. What is the Tree of Life which was the hope of the Israelites of the Old Testament age and of Christians of the New Testament era?
Judging from the fact that the ultimate hope of Adam before the fall was to become a Tree of Life, we can conclude that this is true for man after the fall as well. This is because everything that fallen man truly seeks is what he lost because of the fall. Thus, we find in Gen. 3:24 that Adam, after committing sin, could not reach the Tree of Life and it has since remained the hope of fallen man.