Most people think of eternal life as beginning at the point of mortal death. Of course, our entrance into the presence of God does occur at death, and we get a new body at the resurrection. But, in many tangible ways, our eternal life actually begins when we place our faith in Christ. It could be said that in some ways, for believers, eternity is now.
The Apostle Peter describes it this way: "His (Jesus Christ's) divine power has given us everything we need for life and godliness through our knowledge of him who called us by his own glory and goodness. Through these he has given us his very great and precious promises, so that through them you may participate in the divine nature and escape the corruption in the world caused by evil desires." (2 Peter 1:3-4)
Much of what it means to be a believer is found in God's power and promises. We have hope of heaven because of his power and promises. We are to live with a confident expectation that God has the power to fulfill every promise he has made to us. This hope is based on faith, and confirmed in our hearts by the Holy Spirit. The proof of our eternal life is God's presence in our lives today. Eternity can and should be a reality for every believer.