Job 32:8-9 ESV

But it is the spirit in man,

    the breath of the Almighty, that makes him understand.

It is not the old who are wise,

    nor the aged who understand what is right.

Proverbs 2:3-5 NKJV

Yes, if you cry out for discernment, And lift up your voice for understanding, If you seek her as silver, And search for her as for hidden treasures; Then you will understand the fear of the Lord , And find the knowledge of God.

Proverbs 2:10-11 NKJV

When wisdom enters your heart, And knowledge is pleasant to your soul, Discretion will preserve you; Understanding will keep you,

The demons generally produce in us the opposite of what has just been said. For when they take possession of the soul and extinguish the light of the mind, then there is no longer in us poor wretches either sobriety, or discernment, or self-knowledge or shame; but there is indifference, lack of perception, want of discernment and blindness. 

What has just been said is known very vividly by those who have subdued their lust in order to become chaste, who have curbed their freedom of speech and have changed from shamelessness to modesty. They know how after the sobering of the mind, after the ending of its blindness, or rather its maiming, they are inwardly ashamed of themselves for what they said and did before when they were living in blindness.

—St. John Climacus, The Ladder of Divine Ascent

You might look at someone and judge them – maybe they’re living a sinful life, maybe they’re struggling with a sin that brings more shame than others – and you’re judging them without discernment knowing that if you lived a day in this person’s life, you would never be able to fight the sin that they’re fighting with daily.

—Fr. Paul Girguis

Offer to those who visit you what is necessary both for the body and for the spirit. If they are wiser than we are, let us show our philosophy by silence. And if they are brethren following the same way of life, let us open the door of speech to them in due measure. Yet it is better to regard all as superior to us.

—St. John Climacus, The Ladder of Divine Ascent

Do not say: ‘I do not know what is right, therefore I am not to blame when I fail to do it.’ For if you did all the good about which you do know, what you should do next would then become clear to you, as if you were passing through a house from one room to another. It is not helpful to know what comes later before you have done what comes first. For knowledge without action ‘puffs up’, but ‘love edifies’, because it ‘patiently accepts all things’ (1 Cor. 8:1; 13:7). 

—St. Mark the Ascetic

The Fathers forbid us to give advice to our neighbor on our own accord, without our neighbor’s asking us to do so. The voluntary giving of advice is a sign that we regard ourselves as possessed of spiritual knowledge and worth, which is a clear sign of pride and self-deception.

—Bishop Ignatios, The Arena: An Offering to Contemporary Monasticism

From this it follows that leaving the world is nothing other than cleaning up your entire external life, removing from it everything passionate and replacing it with something pure, which will not disrupt the spiritual life, but rather aid it.  Be it in family, personal or social life—completely re-order your outward behavior in and outside the home, with friends and associates, as the spirit of your new life requires it.  Establish rules and order in every part of the home, at work, with acquaintances, and when, how and with whom you spend your time.

How can this be done?  However you can, only do it with counsel and discernment, according to the guidance of your spiritual father, or someone you trust.  Some people do this suddenly, and it seems better, while others do it by degrees.  Only, from the first minute you should come to hate with all your heart everything worldly and sinful, and estrange yourself from it, not wanting it or delighting in it.  Do not be conformed to this world (Romans 12.2).  After inwardly abandoning the world, visible departure may follow either suddenly or gradually.  A man who is weak in spirit will not bear a long drawn-out abandonment—he will not stand firm, will weaken and fall.  Such ones are especially overcome by passions of the flesh, which are like second nature to him.  Therefore such people should always leave it all suddenly, going far away from that place where they wallowed in sin.  A man strong in the spirit of zeal will bear it even by degrees.  But for the former as well as the latter, it is absolutely necessary from the first moment of conversion to cease all association with the sinful world and everything worldly until the form of new life has been established.  This is the same as fencing around a transplanted tree; for though the wind be soft, it could blow the tree over because its roots are still weak.

St. Theophan the Recluse, The Path to Salvation: A Manual of Spiritual Transformation

Regarding the universally praised experience in discerning thoughts, that is, which ones to carry out and which ones to turn away, there can be no rule for this.  Let everyone learn himself from his own experience, for we never meet a man whose rules always apply to us.

St. Theophan the Recluse,The Path to Salvation: A Manual of Spiritual Transformation