“I know well that the greater and more beautiful the work is,
the more terrible will be the storms that rage against it.”
St. Faustina
(wavebreak media)
“Throughout Sacred Scripture,
we find that when God’s people fast, the power of their prayers is increased,
especially when they are engaged in spiritual warfare.
In the Old Testament,
the Lord told Isaiah that a fast properly undertaken would
‘loose the bonds of wickedness…undo the thongs of the yoke…
let the oppressed go free’ (Is. 58:6) …
In the New Testament,
we find that Jesus fasted for forty days and nights in the wilderness
in preparation for His battle with Satan, who came to tempt Him
(see Lk 4:1-2)…
If prayer is a spiritual weapon, fasting is the spiritual whetstone on which it is sharpened.
It’s the spiritual muscle that, when exercised regularly,
strengthens the thrust of that weapon to pierce the Enemy and drive him away.”
Paul Thigpen, p. 42
An Excerpt From
Manual for Spiritual Warfare
cookiecrumbstoliveby 
I have personally found this to be true.
🙂