Do sacraments protect a person against evil?

Sacraments and sacramentals undoubtedly protect us from the power of evil but not because they are magic.  They are, rather, spiritual fountains which confer grace, provided that the recipient of these marvelous gifts uses or receives them with faith.  The "protection" of the Church's spiritual resources can be likened to an electrified fence around a house.  The grace that flows into a person's life through these channels is like the electricity flowing through the wires of that fence.  Without the electric current, the fence is still a barrier of sorts but with less protection against an invader.  So also, without faith, the sacraments and sacramentals do very little to protect us from the power of evil spirits.

By Fr. Thomas J. Euteneuer "Exorcism and the Church Militant" page 46, question 32.