On this Feast of St.Michael the Archangel, our thoughts are raised towards the reality of spiritual warfare. St. Teresa of Jesus has this to say:
"I am certain that those who seek perfection do not ask the Lord to free them from trials or temptations or persecutions or struggles. This is another very great and certain effect of the contemplation and the favors His Majesty gives and of the Lord's Spirit rather than of an illusion...These persons desire, ask for, and love trials. They are like soldiers who are happier when there are more wars because they then hope to earn more. If there is no war, they receive their wages but realize they won't get rich.
"Believe, sisters, that the soldiers of Christ, those who experience contemplation and engage in prayer, are very eager to fight. They never fear public enemies very much; they already recognize them and know that their enemies have no power against the strength the Lord gives and that they themselves always come out victors and with much gain. They never turn from these enemies. Those whom they fear...are the traitorous enemies, the devils who transfigure themselves into angels of light, who come disguised. Not until they have done much harm to the soul do they allow themselves to be recognized. They suck away our blood and destroy our virtues, and we go about in the midst of the same temptation but do not know it. With regard to these enemies, let us ask and often beg the Lord in the Our Father to free us and not let us walk into temptation, so that they will not draw us into error or hide the light and truth from us, that the poison will be discovered...
"Consider, daughters, the many ways these enemies can cause harm. Don't think that they do so only by making us suppose that the delights and consolations they can feign in us are from God. This seems to me the least harm...they can cause: rather it could be that by means of this they will make one advance more quickly. For, in being fed on that delight, such a person will spend more hours in prayer. Since he doesn't know that the delight is from the devil and since he sees he is unworthy of these consolations, he doesn't stop thanking God. He will feel greater obligation to serve Him and, thinking the favors came from the hand of the Lord, he will strive to dispose himself so that God will grant him more.
"Strive always, sisters, for humility and to see that you are unworthy of these favors; do not seek them. I hold that the devil loses many souls who strive for this humility. He thinks he is going to bring them to perdition, but the Lord draws good from the evil the devil aims at. His Majesty looks at our intention, which is to please and serve Him and remain with Him in prayer; and the Lord is faithful. It's good to be on one's guard lest there be a break in humility, or some vainglory emerge. If you bessech the Lord to free you from this, do not fear that His Majesty will allow you to be favored very much by anyone other than Himself.
"The way the devil can do a great deal of harm, without our realizing it, is to make us believe we have virtues when we do not. This is a pestilence. In regard to the delights and consolations, it seems merely that we are receiving and that we have the greater obligation to serve. In regard to our thinking we are virtuous, it seems we are serving and giving and that the Lord is obliged to pay. Thus little by little this latter notion does great harm. On the one hand, it weakens humility, and on the other hand, we grow careless about acquiring that virtue which we think we have already acquired. Well, what is the remedy, sisters? That which seems best to me is what our Master teaches us: prayer and supplication to the Eternal Father not to let us enter into temptation.
St. Teresa of Jesus, The Way of Perfection, XXXVII, 1-5.