To be dead in your sins is to be alive in body yet asleep in spirit, moving through your days run by old conditioning, reacting without ever being present. It is a kind of sleep, a life lived entirely in the head, cut off from the aliveness of this moment.
To be quickened is to wake up. Something in you comes alive that was dormant, and you feel the presence that was always underneath the thinking. And the past, all those trespasses, loses its grip, because a self that lives fully in the present is no longer carrying and defending the story of what it did. You come alive, and the weight of the past falls away.