The disciples already have commenced eternal life. To trust Jesus and His God is to begin that life now. Today we taste and see that God is good . Those who believe have already passed from death to life . Caught as we are in the limitations of the here and now, eternal life is only a small foretaste, but it is the real thing.
Eternal life is now.
The most significant joy of eternal life is love. Love, love and more love. As does also the first Letter of John. Love is the litmus test. Love of God, love of each other.