"11Likewise reckon ye also yourselves to be dead indeed unto sin, but alive unto God through Jesus Christ our Lord." (Romans 6: 11)
Man is born into this world "dead in his trespasses" (Ephesians 2: 1).
This death is more than the cessation of life, obviously, since man comes out the womb crying, breathing, and moving about, and does more of the same throughout his assigned seventy years of life on the Earth.
The death is separation from God.
In the beginning, when God made Heaven and Earth, He then made man in His own image, to foster a perfect oneness and relationship which would never end.
Adam and Eve sinned when they deliberately stepped out of simple, holy dependence on God. By partaking of the fruit of the Tree of the Knowledge of Good and Evil, the Spirit of God left the first man and woman. They were then driven from the Garden of Eden, for if they ate from the Tree of Life in their fallen, dead and separated state, God would have had no choice but to leave them to a state of eternal death.
Man is separated from God, which creates a sense of loneliness, alienation, frustration, anger, and unease unending in man.
We need to belong, we need to identify with something, someone, or somewhere, and inevitably man begins to identify with just about anything that he can find. Whether a gang, his family, his work, his accomplishments, his own skin, he searches in desperation to found himself on something.
Yet no matter what he does, what he says, what he has, the emptiness, the death, the loss, the alienation cannot be removed.
We are dead in our trespasses, and only the Life of God Himself living within in us can restore and flourish man once again.
The fear of separation, the need to "do something" in our lives, the sense of "not measuring up" that dogs man stems from our initial separation from God.
God desperately wants to live in us, but the sin which we have inherited from Adam cannot go unpunished.
So, God sent His Son, His darling, His Beloved, to die for us, so that we may receive not only eternal forgiveness for all our sins, both the one in which we are born, and the ones which we commit, but now God can place His Life, His Son, Himself, to live within us, too.
Paul exhorts everyone of us to "reckon" or accept as accomplished that we are dead to sin, the condemnation and separation, and instead to see ourselves as alive to God in Christ.