The Holy Spirit enables man to fulfill his calling as a creature of God

The Christian Church lives by the Holy Spirit. The Spirit alone is the guarantee of God’s Kingdom on earth. He is the sole guarantee that God’s life and truth and love are with men. Only by the Holy Spirit can man and the world fulfill that for which they were created by God. All of God’s actions toward man and the world—in creation, salvation and final glorification—are from the Father through the Son (Word) in the Holy Spirit; and all of man’s capabilities of response to God are in the same Spirit, through the same Son to the same Father.

Thomas Hopko
From the Series: The Orthodox Church
Volume I – Doctrine and Scripture: The Symbol of Faith

Virtue is a gift from God — man is not capable.

Consider how [Jesus Christ] teaches us to be humble, by making us see that our virtue does not depend on our work alone but on grace from on high. He commands each of the faithful who prays to do so universally, for the whole world. For he did not say “thy will be done in me or in us”, but “on earth”, the whole earth, so that error may be banished from it, truth take root in it, all vice be destroyed on it, virtue flourish on it, and earth no longer differ from heaven.

St. John Chrysostom
On the Lord’s Prayer

Liberty only leads man further into sin

It is a remarkable phenomenon in nature that, if you put a plant into a large, wide pot or tub, it grows very much at the roots; they thicken, they give out many ramifications, but the tree itself does not grow much in height, and only yields few and small leaves and flowers. But if it is planted in a small pot, then the roots are small, but the plant itself grows rapidly in height and yields beautiful leaves and flowers (if it is the nature of the plant to produce flowers). Is it not the same with man? When he lives in full liberty, in abundance and prosperity, then he grows in body and does not grow in spirit, does not bring forth fruits — good works; whilst when he lives in straightness, in poverty, sickness, misfortune, and afflictions, in a word, when his animal nature is crushed, then he grows spiritually, bears flowers of virtue, ripens and brings forth rich fruits. This is why the path of those who love God is a narrow one.

St. John of Krondstat
On Good Works

We are nothing without Christ. All our good is His Good.

I am morally nothing without the Lord. I have really not one true thought or good feeling, and can do no good works; without Him I cannot drive away from me any sinful thought, any passionate feeling such as malice, envy, fornication, pride, and so forth. The Lord is the accomplishment of everything good that I think, feel, and do. O, how boundlessly wide is the Lord’s grace acting in me! The Lord is everything to me, and so clearly, so constantly. Mine — is only my sinfulness; mine — are only mine infirmities.

St. John of Krondstat
On Good Works

Works cannot merit salvation

When the foolish thought of counting up any of your good works enters into your head, immediately correct your fault and rather count up your sins, your continual and innumerable offenses against the All-merciful and Righteous Master, and you will find that their number is as the sand of the sea, whilst your virtues in comparison with them are as nothing.

St. John of Kronstadt
On Good Works