Eternity versus a few years of living on Earth. Let's just say you don't believe in God or His Savior Son, Jesus. The End.
“By faith Enoch was taken from this life, so that he did not experience death: ‘He could not be found, because God had taken him away.” For before he was taken, he was commended as one who pleased God. And without faith it is impossible to please God, because anyone who comes to him must believe that he exists and that he rewards those who earnestly seek him.” Hebrews 11:5-6 (NIV) (emphasis mine)
Read Hebrews 11 in its entirety.
What does it mean to have a personal relationship with God? Read here.