If knowledge about exorcisms had been passed down from one generation to the next, then beside the votary priest there would be another priests - the master exorcists who would have many years' experience of exorcisms. He would have taught the novice, encouraged him, but above all would have cleansed him when he was possessed during the instruction. In the history of the Church there were only a few who felt the need to practice exorcism. Hundreds of people begging for help came to their door. There were, however, so few of them that they collapsed with exhaustion wanting to help them all. They had nowhere they could find models so they acted by trial and error. Many of them fell victim to possession and needed an exorcism themselves. Another priest wasn't at such case always able to help. Often he was unable to do so, and seeing his colleague's fate was afraid for his own safety. These exorcists were like lone sailors left to themselves and often ridiculed for their work.
Whether or not a priest will become an exorcist at all let alone a good one depends in large measure on the ghost which has possessed a person. If it wanted to leave after the first session then the priest scored a success and acquired faith in his abilities to do it. With every successful case it became easier for him even if he suffered a setback. An exorcist priest who fails at the first step will soon lose his enthusiasm. He may even want very much to become an exorcist and to help people but when he constantly fails he loses faith in what he's doing for ever. Discouragement may also be the result of a conviction that he is fighting against something powerful which he will never overcome. It may not even occur to him that it was only the way in which he carried out the exorcism that was unsuccessful. Either way, a defeat brings about a lack of faith in what the church exorcists are doing. Often horror starts to creep in, too. The ghosts not only refuse to leave but they also try to frighten the priest more and more. That's why many exorcist priests give it up, and many others watching them don't even start on exorcisms. Many priests are frightened of the devil, his vengeance, and they also fear possessed people. In such cases it is easier to ascribe mental diseases to every symptom and to send the patient off to a hospital just to have at least one case taken off one's hands. But these instances do not diminish, there are more and more of them.
“Possessed by Ghosts - Exorcisms in 21st Century”