To speak theologically about sin means to try to grasp a very ambiguous and liquid phaenomenon with a basically parasitic existence: sin cannot exist on its own, it always perverts something positive or neutral. Therefore on one side, it is to speak about sin as about human acting, but on the other side and at the same time as about a certain power over humans.
The theological talk about sin runs at the end into the confession of sin as one's own sin and ends with a fundamental change of perspective so that the point of hamartiology is not theoretical, but practical.