What comes first, the chicken or the egg? Tricky! Without a chicken you can't have an egg, but then, without an egg you cannot have a chicken.
The same case can be made for temporal and eternal life. God designed the temporal life for the spiritual reality of eternal life and the promise of eternal life is born out of the physical reality of temporal life.
God's promise of the afterlife is inextricably interwoven with how we live out our present life. Always keep that in mind so that, when you make choices in life, you do it against the backdrop of the promise of eternal life.