Spiritual heroes come to light at the time of despondency

Venerable John Climacus ~ The Ladder of Divine Ascent
Step 13 ~ On Despondency

¶12. Spiritual heroes come to light at the time of despondency, for nothing procures so many crowns for a monk as the battle with despondency.

A courageous soul resurrects his dying mind

Venerable John Climacus ~ The Ladder of Divine Ascent
Step 13 ~ On Despondency

¶9. Each of the other passions is destroyed by some particular virtue. But despondency for the monk is a general death.
¶10. A courageous soul resurrects his dying mind, but despondency and sloth squander all his riches.

Despondency is a paralysis of soul

Venerable John Climacus ~ The Ladder of Divine Ascent
Step 13 ~ On Despondency

¶2. Despondency is a paralysis of soul, an enervation of the mind, neglect of asceticism, hatred of the vow made. It calls those who are in the world blessed. It accuses God of being merciless and without love for men. It is being languid in singing psalms, weak in prayer, like iron in service, resolute in manual labour, reliable in obedience.

Do not give in to despondency

Venerable Seraphim of Sarov

When despondency seizes us, let us not give in to it. Rather, fortified and protected by the light of faith, let us with great courage say to the spirit of evil: "What are you to us, you who are cut off from God, a fugitive for Heaven, and a slave of evil? You dare not do anything to us: Christ, the Son of God, has dominion over us and over all. Leave us, you thing of bane. We are made steadfast by the uprightness of His Cross. Serpent, we trample on your head."

Dealing with dejection and loneliness

St. John of Kronstadt

When you are praying alone, and your spirit is dejected, and you are wearied and oppressed by your loneliness, remember then, as always, that God the Trinity looks upon you with eyes brighter than the sun; also all the angels, your own Guardian Angel, and all the Saints of God. Truly they do; for they are all one in God, and where God is, there are they also. Where the sun is, thither also are directed all its rays. Try to understand what this means.

Do this and you will be saved

Venerable Anthony the Great
The Sayings of the Desert Fathers

¶1. When the holy Abba Anthony lived in the desert he was beset by accidie*, and attacked by many sinful thoughts. He said to God, 'Lord, I want to be saved but these thoughts do not leave me alone; what shall I do in my affliction? How can I be saved?' A short while afterwards, when he got up to go out, Anthony saw a man like himself sitting at his work, getting up from his work to pray, then sitting down and plaiting a rope, then getting up again to pray. It was an angel of the Lord sent to correct and reassure him. He heard the angel saying to him, 'Do this and you will be saved.' At these words, Anthony was filled with joy and courage. He did this, and he was saved.

*accidie - despondency, depression, listlessness

Some plausible pretext to drag us from prayer

Venerable John Climacus ~ The Ladder of Divine Ascent
Step 13 ~ On Despondency

¶7. [Despondency] reminds those standing at prayer of necessary duties. And, brutish as she is, she leaves no stone unturned to find some plausible pretext to drag us from prayer as with a kind of halter.