Fear and doubt are states of the mind.
Love, peace, faith and trust are states of the heart.
Fear and doubt are deception methods used by Satan to cloud our minds from growing spiritual love and trust in God.
God's perfect "Love" casts out fear and lets peace and love settle in our hearts. Likewise,
trust in God's "Truth" casts out doubt and lets faith and trust build in our hearts.
Faith is not a grace we can ask for. It is built up slowly over time as our spiritual doubt decreases and our trust increases through our prayers and life experiences.
Because doubt is a state of the mind influenced by Satan, we can use powers greater than him to rebuke his actions and free our minds of doubt.
"I rebuke my doubt in the
name of Jesus.
Bind my doubt and release it
from its stronghold.
God has not giving me a spirit of doubt, but of power, and of "truth" and of a sound mind.
I have God's perfect "truth", and that perfect truth cast out doubt."
Replete as necessary.
Best said in the presence of the Holy Eucharist.
The Essential two-minute Prayer Page
Rebuking Inadequate feelings