Sometimes in nature a warm, healthful wind blows, pleasantly and lightly, permeating and coming in contact with the body, and the sky is serene; whilst at other times a cold wind blows, one feels, somehow, distressed and feverish, the wind pierces to the very bones and affects the body unpleasantly, the earth and sky are darkened; or else sometimes the state of the atmosphere is warm and warmth-giving, and at other times cold, benumbing. It is likewise in the spiritual life: sometimes our soul is surrounded and penetrated by a light, pleasant, warmth-giving, vivifying breath, we feel ourselves happy and tranquil; whilst at others our heart is touched by a heavy, deathly breath, accompanied by complete spiritual darkness. The first state proceeds from the Spirit of God, the second from the Devil. It is necessary to accustom ourselves to everything: as in the first case, not to grow self-conceited, so in the last, not to fall into despondency, into despair, but to fervently have recourse to God.
St. John of Kronstadt
The Beautiful Path 