Sometimes a demon will leave quietly, and you will know by the gift of discerning of spirits that they have gone. When we are driving out spirits, we are not on our own. We depend on God for revelation, and he usually guides through the whole process. Another way to know that a spirit has left is that the trouble the demon caused has ceased. The more we pray over the demonized, the better we will become at it. Everyone makes mistakes in praying for the demonized, especially at the beginning. Overzealous