Sin is like a handcuff

"Advent does not offer freedom to the man who is convinced he is already converted.  Stir up thy power: by the help of grace.  It is a case of God against sin.  Sin is very like a handcuff -- only the person with the key can unlock it.  It doesn't matter how fervently I desire it, I cannot rid myself of my handcuffs because I have no key.  And sin is like the door of my cell - even if I had a key I could not unlock the door because it has no keyhole on this side.  It can only be opened from the outside."

- Fr. Alfred Delp SJ, “The Prison Meditations of Father Alfred Delp”, 1963 Herder and Herder New York
See also: The Prison Meditations of Father Delp