Prayer acts murderously on our ‘old man’, the unregenerate self or nature. As long as it is alive in us, it opposes prayer like death. Fallen spirits, knowing the power of prayer and its beneficial effect, endeavor by all possible means to divert us from it, prompting us to use the time assigned to prayer for other occupations; or else they try to annul it and profane it with mundane distractions and sinful inattention, by producing at the time of prayer a countless swarm of earthly thoughts, sinful daydreams and reveries, imaginings and fantasies.
~Ignatius Brianchaninov
Prayerful Life 