In a more subtle way than the possession in our passage today, each of us too can be possessed by the initially small, subtle toe holds we allow evil to gain in our day-to-day life (e.g. anger, envy, grudges, us v. them politics, etc.).
Our long journey, our very personal collaboration with God, to be more Christ-like is a long-term, gradual, non-linear exorcism/healing in slow motion.