Train yourself to cut off an intrusive thought immediately…Be at pains over this, so that you acquire the habit. The soul is a creature of habit: according to the habit you have acquired, so will you act all the rest of your life.
Be careful not to neglect the small things, take care not to despise them as something insignificant. They are not insignificant; they are cancer for the soul, a bad habit. Let us therefore be vigilant. Let us pay attention to slight things, whilst they are still slight and before they become serious. Both the life of holiness and the sinful life start from little things and lead to greater ones, either good or bad.
Without podvig there is altogether no true Christianity, that is to say, Orthodoxy. See what Christ, the First Ascetic, Himself clearly says; 'Whosoever will come after Me, let him deny himself, and take up his cross, and follow Me' (Mark 8:34). The true Christian, the Orthodox Christian, is only he who strives to emulate Christ in the bearing of the cross and is prepared to crucify himself in the Name of Christ. The holy Apostles clearly taught this. Thus the Apostle Peter writes: 'If when you do well and suffer for it, ye take it patiently, this is accepted with God. For even here unto were ye called, because Christ also suffered for us, leaving us an example, that we should follow his steps' (I Pet. 2:2-21). In precisely the same way the holy Apostle Paul says repeatedly in his epistles that all true Christians must be ascetics, and the ascetic labor of the Christian consists of crucifying himself for the sake of Christ: 'They that are Christians have crucified the flesh together with the passions and lusts' (Gal. 5:24). A favorite expression of St. Paul is that we must be crucified with Christ that we might rise with Him.
You write that after Communion you felt well. Glory be to God, Who comforts our unworthiness. And as regards the fact that this soon passed, here also is seen His fatherly providence for us. For continual consolation enfeebles the soul and makes it slothful, or leads to even greater harm. That is why the Lord takes it away quickly and again makes us feel our weakness, our helplessness, and our sinfulness. We must humble ourselves more, reproach ourselves, offer repentance for our sins, and not desire consolations, but patiently endure what God allows. Dryness and cooling of fervor are also permitted on account of vainglory.
Habit forms from custom, and habit seems to accustom itself to nature. It is much worse and more difficult to change nature. However, with God it is possible. For nature does not set itself against God.
In the eyes of God, it is always preeminently right that a man should spend himself in devising new means for spreading consolation to his subordinates, who are his charges.