In his book, Vatican exorcist talks about the importance of sacred images and sacramentals to drive out evil spirits.  It should  not  act as a "good luck charm".  The faithful must  seek  the protection of those that are personified in the sacred medals.

"One of the most famous instances of diabolical possession , which many books report, thanks to the accuracy of the historical documentation, concerns two brothers, the Burners.  The two brothers were freed in 1869, following a series of exorcisms.  It is reported that among the many , extremely vicious, actions of the demon was a plan to overturn the coach that transported the exorcist, a monsignor and a nun.  The devil was foiled in his intent only because the coach driver, at the last minute, was given a medal of St. Benedict to protect him on the journey, and the good man devoutly put it in his pocket."

Source:  Fr.  Gabriele Amorth, "An Exorcist Tells His Story"