Philokalia

When our intellect begins to sense the grace of the Holy Spirit, then Satan too pretends to console the soul with a certain sense of false sweetness (ἡδυφανεῖ) in the quiet of the nighttime, when one is drowsy and dozing lightly. But as long as the intellect continues in deeply fervent remembrance of the holy name of the Lord Jesus and avails itself of this holy and glorious name as a weapon against Satan's deceit, the deceiver will abandon this stratagem and from then will try to incite the soul to sin directly. From this the intellect learns to recognize clearly the deceit of the evil one and progresses further in the virtue of discernment by experience.”

And again, “The good and divine consolation manifests itself while the body is awake or on the verge of falling asleep, while one is cleaving to God’s love in the fervent remembrance of Him. But a delusional consolation comes to the ascetic, as I have said, while he falls into a kind of doze in half-hearted remembrance (μετὰ μέσης μνήμης) of God. True consolation, since it is from God, manifestly consoles the souls of those who struggle in piety and they are drawn to the love of God through a great outpouring of love in the soul. False consolation, on the other hand, tends to buffet the soul with the winds of error, and by means of bodily sleep it attempts to snatch away the experience of spiritual perception from an otherwise healthy intellect, especially while it happens to be lukewarm in its remembrance of God. But as long as the intellect is found in an attentive state of remembering the Lord Jesus, it will be able to scatter the enemy's seductive aura and to engage in spiritual warfare against him undismayed, armed with another weapon alongside divine grace: the confidence derived from experience (τὸ ἐκ πείρας καύχημα).  

“Occasionally the soul, free from doubt and fantasies, is kindled and moved toward the love of God, so that it even draws the body into the depths of this ineffable love, which sometimes happens in the way I explained, that is, while the person is awake or beginning to enter a sleep brought on by God's grace, and while the soul is thinking of nothing but the blessed end towards which it is moving. In this case we should know that this is the energy of the Holy Spirit. For when the soul is completely delighted by that inexpressible sweetness, it can bring to mind nothing else, since at that moment it rejoices with an insistent joy. However, if the intellect actively conceives any doubt or impure thought, even while it is availing itself of the holy name of Jesus as a defense against evil and no longer just for the love of God, one must understand that this is false consolation from the deceiver, which comes only in the guise of spiritual joy. This counterfeit joy, which is altogether formless and disordered, is a trick of the enemy used to lead the soul into fornication (μοιχεύεσθαι) with him. For when he sees the intellect proudly boasting in its experience of spiritual perception, that is precisely when he seduces the soul by means of seemingly beneficial consolations, in order for it to be distracted by that spongy and slimy (χαύνης … καὶ καθύγρου) pleasure and remain unaware of its unholy union with the deceiver. By this we shall know the spirit of truth and the spirit of error (1 Jn. 4:6). At any rate, it is impossible for someone to be aware either that he is tasting divine goodness (cf. Ps. 33:9) or that he is being tempted by the bitterness of demons, unless he has full assurance (ἑαυτὸν πληροφορήσει) that divine grace dwells in the depths of his intellect, while wicked spirits can only loiter around the outer parts of his heart. This is what the demons do not want people to discover, lest our intellect come to a clear understanding and we wage war against them with the remembrance of God as our mighty weapon.”

Excerpt From

Philokalia Volume 5