God loves you so much that He has given you the free gift of eternal life. You only have to accept it the way you would accept any gift from a friend or loved one. You don't need to wait for eternal life. It starts the moment you give your life to God by accepting Jesus as your Lord and Savior. You don't need to do anything to earn it, because it is already yours.
Some people are unsure, hoping that they have eternal life, but often doubting it.
Here, the apostle John assures us that we can be certain about this, based on God's promise that eternal life is ours through His Son Jesus. You have it regardless of how you feel. Eternal life is based on facts, not feelings. You can know that you have eternal life if you believe God's truth. If you have genuinely committed your life to Jesus as your Savior and Lord, you know by faith that you are indeed a child of God.