Regrettably, it IS one or the other. You've demonstrated Cassian's viewpoint-the "point of decision". This was exactly his position. It is the Catholic's position and the Arminian's position. God opens the heart but people have a right to refuse.
Augustine's position would be that God opens the heart and when one sees and understand the truth, they repent. They do this on their own accord and will. But they repent for they see and understand the glory before them. This is why we say Christians are "called" by God.