The Gospel of John opens by describing just who Jesus is. We find here one of the most stunning revelations about the Son of God, that in Jesus is Life, and that Life is the light of all mankind. This seems to work to qualify the statement immediately before it, which states that everything in our Universe was made by Him and that if Jesus did not make it, it was not made! WOW! Later, in John 14:6, Jesus states outright that He is the Life! Now, if Jesus was with God in the beginning and IS God, and has created all things, and if He is Life, and His Life is the light of all mankind, then it is safe to say that mankind was created to be connected to His Life.
Remember, mankind was originally created perfect, and once walked and talked with God face to face, as we do with our friends. He created mankind with His Life, and to be sustained with His Life. Now, God also purposefully created mankind with free will so that we could have the chance to choose to love Him. The first man and woman chose to push God away in a naive attempt to advance their own life apart from God. God had warned against it, but they made their choice, pushing God away from them. They pushed away their source of Life.
What is the opposite of life? Death. If God is Life, then separation from God is death.