We should also note something very interesting. Right after they sinned, Adam and Eve took care of their shame by sewing fig leaves together. When God handles it, He gives them leather garments. On our own we can accomplish things, like sewing fig leaves. However, when we let God help us he can turn our accomplishments into far better achievements.

Regarding the thorns and thistles that remind us so much of Christ’s crown of thorns, here is what Tim Gray says: “Jesus, like Adam before Him, is tested in a garden, the garden of Gethsemane. When Jesus is praying to the Father for strength to accept the bitter cup of suffering, He prays so intensely that "his sweat became like great drops of blood falling down upon the ground" (Lk. 22:44). As one of the curses for original sin, Adam would labor by “the sweat of his face" (Gen. 3:19). Luke carefully points out how the beads of Jesus' blood fall down upon the ground, the ground which was cursed because of Adam. In fact, part of Adam's curse is that the ground would bring up thorns (Gen. 3:18), and significantly enough Jesus is crowned with thorns (cf. Mt. 27:29; Mk. 15:17). Jesus takes up the agony of Adam through His Passion." Tim Gray, Mission of the Messiah. Emmaus Road p149-150

Verse 22:Then the Lord God said: "See! The man has become like one of us, knowing what is good and what is bad! Therefore, he must not be allowed to put out his hand to take fruit from the tree of life also, and thus eat of it and live forever."
In the Hebrew mindset, death is where there is no praise of God, because a person is cut off from communion with the Author of Life. In this perspective God's banishing Adam and Eve from the garden was actually an act of kindness. He did not want them to live forever physically in a condition of separation from him - a living death that would have been hell on earth. - Mary Healy on Verse 22, Men and Women Are from Eden (By clicking on the title, you can buy this wonderful book!)

For the Jews, death means being spiritually cut off from God, rather than a physical death.
If Adam and Eve had stayed in the Garden of Eden in their state of sin, and had eaten of the fruit of life and lived eternally cut off from God, it would have been terrible for them. Similar for us, being in hell where you are cut off from God totally and definitively is terrible. Both are states of eternal hopelessness. 
God was actually showing His love by sending them away from Eden, far from the tree of life, so that he could rescue them by sending His son and giving them a chance to come back to Him.
God initiates the road towards forgiveness and healing. God does not cease to provide for His children, even though they turn away from Him. Despite their recent sin Adam and Eve are clothed by the Lord! This love and care reflects the bridal imagery shown throughout the Old Testament -- even when Israel is an unfaithful bride, the Lord is a faithful bridegroom.  He always will be.