Prayer Against Evil Thoughts

O God be not far from me.
O my God make haste to help me.
Great fears and imaginings of all kinds have combined to attack my soul.
How can I come through them unharmed?
How can I crush them?

  "I will go before you," says the Lord, "and will humble the great ones of earth.
   I will open the doors of the prison, and will reveal to you hidden secrets."
  O Lord, do as you say and may all my evil imaginings flee from your presence.
  My only hope and comfort is to take refuge with you in all my troubles; to trust you, to call out to you from my inmost heart and patiently wait until you send your comfort.

Amen

Thomas a Kempis, in his magnificent spiritual work,
The Imitation of Christ, offers up many
helpful prayers including this prayer.