Those who by God’s permission tempt us either inflame the desiring aspect of the soul, or stir up its incensive power, or darken its reasoning faculty, or envelop its body in pain, or deprive us of bodily necessities.  (St. Maximus the Confessor, Four Hundred Texts on Love: Second Century)
Here saint Maximus sets side by side for us on the one hand the tripartite division of the soul of man, the mental world of man, and on the other hand that of the body. He is not dealing with man’s personality, but with his passive aspect, with the passions which he may have, bring into activity or suffer.
The phrase by God’s permission means according to the knowledge and permission of God, God allows something to happen to them. Those who by God’s permission tempt us either inflame the desiring aspect of the soul, in other words, they create a burning desire within man, or stir up its incensive power, they contribute to man losing his mental or emotional balance so that he loses his internal peace, creating internal agitation, or darken its reasoning faculty, or they create conflict in the reason [logos], in the reasoning faculty of the soul [logistikon], which ceases to think correctly, so that my reasoning [logismos] is blinded, thrown into a torpor, dulled, distorted; it sees black as white and white as black.
First, we need to interpret at length the phrase either inflame the desiring aspect of the soul. The only thing I am able to desire is God. Is this possible? Of course it is. Because, in reality, the only thing that I am able to know is God. When my intellect [noesis] is absorbed by God, then my spirit is free to ascend together with my soul which is totally given over to God, in addition to my desiring faculty. Consequently, my desire is sincere before God, it is divine, when my mind cleaves to God; otherwise, my internal world suffers a kind of division which can throw a shadow over me, create composition, division, even further fragmentation in my soul so that I am unable to love God, because I am not simple like God is simple.
How can those tempting inflame the desiring faculty of the soul? For example, while I am in a cenobitic monastery, they give me the longing to go out into the desert. They kindle in me this longing, this desire, which seems as if it were from God, but may actually be a stumbling block for me, my fall for the rest of my life. Or, they place in me the desire to go cultivate the people of God, to speak to the people, to save them. How? My heart is filled with warmth, I love them, I want to help them, and this warming [of the heart] is a temptation permitted by God, because God never tempts, he only allows temptations. This is why we say “by God’s permission.” And so my fervent desire is a clear temptation and as much as it takes the form of a good service, so the more dangerous it is, because it is all the better hidden from our understanding.
Second, or stir up its incensive power. The incensive power of the soul is the feeling part, where I feel intensely, where I live intensely; it is not desire. When I desire something, I don’t have it but I want it. The spirited faculty is something which I have and live, I feel it, I have laid hold of it. Whatever within us absorbs [our attention], whatever constrains us and possesses us—even our own thoughts—even if it is something completely our own, internal, when this is stirred up, harmony is lost. It is as if man starts to vibrate, he lives in internal turmoil. Think for a moment how when you come into conflict with someone else’s opinion or someone comes into conflict with your opinion; immediately you’re burning inside to prove what you believe. Or think of when you feel someone to be very dear to you and then others come to steal him, to take him in, or he dies. You feel the loss, your whole being is disturbed, your inner peace is lost.
Third, or darken its reasoning faculty. In the spiritual man the reasoning faculty [logistikon] is inactive, because his spirit is led upward. Generally, the intellect [noeron] soars high above, but the reason [logos] slows it dow---it wants to paint, it wants to be occupied, it constrains the intellect [nous]. Hence when we speak about the spiritual life, we distinguish the intellect [noeron] from the reason [logistiko]; while when we speak about the life of the passions and the properties of the soul, we don’t distinguish the intellect from the reason, but the incensive power of the soul at work.
When my intellect [nous] ascends toward God, then reasoning mind [logos], thought is pure and has no content, because the intellect [nous] is empty and is absorbed in God alone. Then the reasoning mind [logos] does nothing else but follows God. In other words, the mind [logos], when it is pure, is one with the intellect [nous]. But when it is not pure, then it becomes a counterweight to the intellect, it darkens the atmosphere so to speak, and the intellect is incapable of continuing on its course. Then we have thoughts [logismoi] as we say which in their most crude form result in fantasy. The intellect [noeron], when it mixes with an unclean thought, is essentially nonexistent, it is an eagle which has fallen in the mud and been covered up. But when the intellect [nous] is an eagle, when the intellect flies, then the Tempter or the people [around us] try to cast a shadow on the reasoning mind [logistiko].
What is the difference between what the demons do on the one hand, and what other people do? They come into conflict with our desires, or they give us desires, and [either method] achieves the same result, warmth; or they help us in our thinking, in what we are living and feeling, or they come into conflict with this, and then cast a shadow on the reasoning faculty, removing its brightness and giving it content like a cloud, something so you can’t see. Any content in the reasoning mind obstructs the vision of God, it isn’t the cloud behind which God [waits], but the cloud above which [waits] the tempter. This is what happens with regard to the soul.
Now, regarding the body, or envelop its body in pain, or deprive us of bodily necessities. If it is the Evil One who is tempting you, he can come and hit you, cover you with bruises, make you sick, or take away all of your possessions. The same things happens if it is the people around you; maybe they fill [your life] with bodily grief, with deprivation, with impotence, hunger, nakedness, with whatever else it may be. In other words, they confine you so that deprived as you are, you can no longer deal with it, you react, and you lose your peace with God.
If you succeed in surpassing the grief, meaning you no longer consider the grief something evil , but only good—if you consider every robbery, loss, and grief as visitations of God—then you have become incapable of being tempted. But from the moment that you want to conquer the grief, the pain, you want to fight back, or to regain any of your lost bodily goods, then you [become] unable to have a relationship with God, or [at least] your relationship is disturbed. For example, you don’t have anything to eat. “I have learned to be content in whatever circumstances I find myself,” says the Apostle [Philippians 4:11]. Do I have anything to eat? I will eat. And if I don’t have anything to eat? I won’t eat. Do I have my health? I will say, glory to Thee, O God. And if I don’t have my health? Again, I will say, glory to Thee, O God. From the moment that I want to become well, to get better from my illness, going to one doctor and then another, doing everything [I can], finding new drugs from America, from Russia, I’ve already lost God; I am a top spinning upon the earth.
The same thing also happens when I’m unable to understand that, whatever I don’t have, I don’t need. They took my clothes from me, my possessions, or my money, they stole my wife, my friend, or my father; this means that they weren’t necessary for me. Loss and grief constitute a criterion of our spirituality. A man who reacts to pain, or who is afraid of pain, or struggles because of the lack or absence of [material] things doesn’t have God—for him, God is dead.
In order for someone to not be tempted and to not lose his contact with God, so that God does not cease to exist for him, in everything regarding the body, he must love pain, grief, and want.
Archimandrite Aimilianos of Simonopetra, Concerning Love: Interpreting St. Maximus the Confessor, p. 87-92 [Translation mine]