Two things that are helpful are a properly blessed (from the Roman Ritual) with its exorcism blessing, the St. Benedict medal.
When troubled by spiritual attacks one can touch it to one's forehead and pray.
Praying a short prayer, aloud, even if only very quietly, such as, "Jesus, Mary, and Joseph, protect us." is also very helpful. The holy names said aloud, prayerfully and devoutly, have great good effect.