Jesus came from the glory of the eternal Trinity to earth as a man.
When He had finished His mission He returned to glory.
But there was glory in the mission. And Jesus completed everything the Father sent Him to do. He died and arose to secure eternal life for those who believe.
In John’s Gospel, Jesus has spoken many times of eternal life. But here in chapter 17 He describes it. Eternal life is knowing the Father and the Son.
Jesus died to secure a relationship. Not just to bring us into a quantity of life that goes on forever, but to bring us into a life of truly knowing our God.