Sin is disobeying God’s law, which is both written on our hearts and spelled out in holy scripture. It is a manifestation of self-centeredness, which is the opposite of what we were created for—to love the God of Israel and to love our neighbors.
Sin makes us less human, obedience makes us more human. So sin is partaking of darkness, drawing out of us the light that is to guide us into being more and more the image of the most loving person every, Jesus of Nazareth.
Sin is what takes life out of us, drawing us more and more into the darkness of nothingness that would have the world believe there finally is nothing beyond blind matter. It is a power that can take over us. The only way to escape its clutches is through the orthodox Church with its fearless preaching of Scripture and its life-giving sacraments.